PRECLINICAL
STUDY
Lymphatic drainage in the muscle and subcutis of the arm
after
breast cancer treatment
Anthony W. B. Stanton Æ Stephanie Modi Æ
Thomas
M. Bennett Britton Æ Anand D. Purushotham Æ
A. Michael Peters Æ J. Rodney
Levick Æ Peter S. Mortimer
Received: 5 September 2008 / Accepted: 17
November 2008
Springer Science+Business Media, LLC. 2008
Abstract Breast
cancer-related lymphoedema of the arm
(BCRL) results from impaired lymph
drainage after axillary
surgery. Little is known about lymphatic changes
in
the arm between surgery and oedema onset. We measured
forearm muscle
and subcutis lymph drainage in 36 women
at 7 and 30 months after surgery by
quantitative lymphoscintigraphy.
None had BCRL initially but 19% had
BCRL
by 30 months. At 7 months muscle and subcutis drainage
in both arms
of BCRL-destined women exceeded that of
non-BCRL women (P\0.01). Muscle
lymph drainage
always exceeded subcutis drainage (P\0.0001). Muscle
lymph
drainage in the ipsilateral arm was unimpaired relative
to the contralateral
arm. BCRL therefore developed in
women with higher peripheral lymph flows.
The major
lymphatic load was generated by muscle; there was no pre-
BCRL
lymphatic impairment in the muscle of the ipsilateral
arm. We propose that
some women have a defined,
constitutive predisposition to secondary
lymphoedema.
Specifically, women with higher filtration rates,
and
therefore higher lymph flows through the axilla that are
closer to
the maximum sustainable, are at greater risk of
BCRL following axillary
trauma, even following removal
of 1–2 nodes.
Keywords Arm Breast cancer
Lymphatic
Lymphoedema Lymphoscintigraphy Lymph
flow
Introduction
Axillary nodal surgery and radiotherapy for breast
cancer
interfere with lymph drainage from the ipsilateral arm. In
21–33%
of women this results in a swelling of the arm,
breast cancer-related
lymphoedema (BCRL), after a delay
of months to years [1–5]. BCRL is
associated with pain,
impaired function, psychological morbidity,
cellulitis,
occasionally skin malignancy, and remains a
significant
clinical problem. There is a perception that the
introduction
of breast-conserving surgery, and sentinel lymph node
biopsy
(SLNB) in particular, has made BCRL a thing of the
past but the evidence
does not support this. After SLNB
alone the incidence is 5–7% [6–8] but the
incidence is
almost certainly higher in patients in whom more than
one
axillary node is removed or in whom a double procedure
(positive SLNB
followed by axillary clearance) is
performed.
A. W. B. Stanton (&)
S. Modi P. S. Mortimer
Cardiac & Vascular Sciences (Dermatology), St
George’s
Hospital Medical School, University of London,
Cranmer Terrace,
London SW17 0RE, UK
e-mail: [email protected]
T. M. Bennett
Britton
Cambridge Breast Unit, Addenbrooke’s Hospital,
Cambridge CB2 2QQ,
UK
A. D. Purushotham
Hedley Atkins Breast Unit, Academic
Oncology,
Guy’s and St Thomas’ Trust, London SE1 9RT, UK
A. D.
Purushotham
King’s College London, London WC2R 2LS, UK
A. M.
Peters
Nuclear Medicine, Royal Sussex County Hospital,
Brighton BN2 5BE,
UK
J. R. Levick
Basic Medical Sciences (Physiology), St George’s
Hospital
Medical School, University of London, London SW17 0RE, UK
P. S.
Mortimer
Skin and Rare Cancers, Royal Marsden Hospital,
Sutton SM2 5PT,
UK
123
Breast Cancer Res Treat
DOI 10.1007/s10549-008-0259-z
The
understanding of the pathophysiology of BCRL was
limited by technical
difficulties in assessing human
lymphatic function. In long-established
lymphoedema,
radiocontrast lymphangiography demonstrated dilated
and
tortuous lymphatics, dermal backflow and extravasation of
contrast
medium [9]. These changes were attributed to
axillary obstruction because
the epifascial vessels (draining
skin and subcutis) run mainly to the
axilla, although some
also anastomose with a scapular collateral pathway
[10],
and the subfascial (muscle) vessels drain exclusively to
the
axilla. The epifascial and subfascial compartments communicate
at the
wrist and elbow [10, 11]. Most swelling is
epifascial, particularly in the
highly compliant subcutis
[12, 13]. Subfascially, swelling is limited by the
tight
enveloping fascia, but the volume of fluid presented to
the
lymphatics each minute may be higher than in the subcutis
due to the
higher density of filtering capillaries in skeletal
muscle. Supporting this
view, estimated lymph flow from
muscle [14] exceeds that from subcutis
[15–17].
Peripheral lymph flow is assessed best by
quantitative
lymphoscintigraphy (QL) in which the fractional
removal
rate, k, of an injected radiolabelled macromolecule is
measured,
representing local lymph drainage rate per unit
volume of tissue fluid [18].
In the subcutis of the swollen
forearm, local lymph drainage is markedly
reduced relative
to the contralateral arm [15, 16]. Lymph drainage is
also
reduced in the forearm muscle, by 31% in arms with 33%
swelling
[14]. There is a graded relation between reduction
in muscle lymph drainage
and severity of the swelling, but
not between reduction in subcutis lymph
drainage and
swelling [14–16]. Lymphatic function in muscle and
subcutis
has not to date been compared in the same patients,
and little
is known of lymphatic function before overt
oedema. Investigation of the
hand subcutis 3 months after
axillary surgery (with no oedema) showed no
local
impairment of lymph drainage [19]. Declining muscle
lymphatic
function may be crucial to the pathogenesis of
BCRL, and we considered that
muscle lymphatic failure
might precede onset of oedema. We therefore
measured
lymph flow in the forearm muscle and subcutis of women
treated
recently by axillary surgery, initially without
BCRL, and repeated the
measurements 2 years later by
which time some had developed
BCRL.
Patients and methods
Patients and assessment of arms
Forty-three
breast cancer patients from St George’s
Hospital, London, the Royal Marsden
Hospital, Sutton,
and Addenbrooke’s Hospital, Cambridge, were
assessed
7.3 ± 2.8 months (mean ± SD) after surgery. Seven of the
43
(16%) were found to have signs of (previously undiagnosed)
incipient arm
oedema (see below) and were
therefore excluded, leaving 36 women aged 61 ± 9
years
(range: 46–81 years) of body mass index (BMI) 25.9 ±
3.8 kg/m2
without detectable BCRL for this study. All
patients had undergone standard
axillary nodal surgery
(mainly level I ? II); none received axillary
radiotherapy.
No patient had other serious disease or was on
Ca2?-
channel blockers or developed cancer recurrence during the
study.
All were right-handed.
The diagnosis of BCRL in the excluded patients and
in
the patients who later developed BCRL was based on
examination for the
clinical signs of oedema, rather than
arm volume alone [20]. BCRL was
considered to be
present in the ipsilateral arm if (1) the subcutaneous
veins
of the ventral forearm and dorsal hand were less visible
than on
the contralateral side; (2) there was a rounding or
fullness in the medial
elbow and distal upper arm regions;
(3) skin and subcutis thickness was
increased; (4) pitting
oedema was present. Arm volumes were measured using
a
Perometer 350S limb volumeter (Pero-System, Wuppertal,
Germany) in 26
patients, and a tape-measure (with calculation
of arm volume from serial
circumferences measured
at 4 cm intervals) in the remaining 10 [21]. The
eventual 7
BCRL patients had had significantly fewer axillary lymph
nodes
excised than the 29 non-BCRL patients (8 ± 3 vs.
15 ± 8, P = 0.032, unpaired
t test); the BCRL group was
6 years younger than the non-BCRL group (57.1 ±
3.3 vs.
63.2 ± 9.2 years at 7 months post-surgery, P = 0.10), had
smaller
primary tumours (17 ± 7 vs. 23 ± 10 mm,
P = 0.13), and had received a
smaller proportion of mastectomies
(14 vs. 21%) as opposed to wide local
excisions.
Every BCRL patient and 21/29 non-BCRL patients
received
breast/chest wall radiotherapy, which may
increase the risk of BCRL [5]. The
BMI of the BCRL and
the non-BCRL groups was almost identical (P =
0.77).
The study was approved by the Research Ethics
Committees,
conformed to the Declaration of Helsinki, and was
approved by
the Administration of Radioactive Substances
Advisory Committee, UK (ARSAC).
The effective radiation
dose was *0.04 mSv per patient. All
participants
gave informed, written consent.
Quantitative
lymphoscintigraphy and time course
of studies
QL was performed on the
forearm in order to measure k
(local lymph flow/volume of distribution of
tracer). The
radiopharmaceutical was human IgG (TechneScan HIG,
DRN 4369;
Mallinckrodt, Petten, Netherlands) labelled with
99mTc (99mTc-HIG).
Radiochemical purity was 99.1%. The
scintillation detectors (Ametek,
Wokingham, UK) were
calibrated for the pulse energy of 99mTc (137–143 keV).
QL
Breast Cancer Res Treat
123
and the theory equating k to lymph
drainage have been
described in detail and reviewed critically [14–18, 22].
The
patients underwent 4 bilateral QL studies; study 1 (at 7.3
months
post-surgery): k in the subcutis, study 2 (within
7 days of study 1): k in
the muscle, studies 3 and 4 (at 30.5 ±
4.0 months): repetition of studies 1
and 2. At 30 months the
arms were assessed again for clinical signs of
oedema.
After 45 min acclimatisation at 23 ± 1C the forearms
were
supported at heart level and an injection point marked
on each ventral
forearm at 390 ± 20 mm from the middle
fingertip and 60 ± 10 mmlateral to
the midline. 99mTc-HIG
(0.2 ml, 0.60 ± 0.08 MBq) was injected
subcutaneously
for studies 1 and 3 or intramuscularly for studies 2 and
4.
The scintillation detectors were positioned *1 mm above
the skin over
each depot. The maximum depot diameter,
31 mm, was\50% of the diameter of
the skin area under the
detector (65 mm) [15]. Acquisitions (duration 100s)
were
performed every 15 min for 3 h. During the intervening
periods the
patient mostly sat but was also allowed to walk
short distances. The arms
and detectors were carefully
repositioned for each
acquisition.
Calculation of k
Counts were corrected for background and
radioactive
decay, according to N = N0e-ct (N corrected counts,
N0
uncorrected counts, c decay constant (0.001923/min), t min
since
injection). The counts remaining in the depot were then
expressed as the
fraction of the counts from the first acquisition,
and the slope of the loge
of the fraction versus time
plot (9100) gave the percentage of the depot
cleared per
minute, k (%/min). The slope was measured from the end of
any
initial lag phase (28–30% of cases, duration*30 min).
Statistical
analysis
Results are shown as the mean ± standard deviation (SD),
with the
range for some results, and the standard error of the
mean (SEM) in the
figures. Groups were compared using
Student’s unpaired and paired t tests,
Wilcoxon’s matched
pairs test for non-Gaussian ratios of subcutis k to
muscle k,
and 2-way analysis of variance (ANOVA). The slope of the
depot
clearance plot was obtained by linear regression.
Analysis was performed
using Prism 4.0 (GraphPad, San
Diego, CA). Significance was accepted at
P\0.05.
Results
Compliance, incidence of BCRL and arm
volumes
Thirty-six women completed studies 1–2, 33 completed
studies 1–3
and 32 completed studies 1–4. Arm volumes at
7 months for the whole group
were similar on the ipsilateral
and contralateral sides (n = 36) (Table 1).
Six patients
were diagnosed with BCRL at 19 ± 5 months (11–23
months)
after surgery. One further patient was found to
have previously unrecognised
clinical signs of oedema at
study 3, giving an overall incidence of BCRL
from 7 to
30 months of 19%. Including the rejected incipient cases,
the
incidence (from 2 months) was 14/43 (32.5%).
At 30 months the
lymphoedematous arm was 5.8 ± 2.0%
bigger than the contralateral arm (n = 7,
P = 0.0007, paired
t test) (Table 1). The difference in arm volume was
due
partly to ipsilateral swelling and partly to a 2.2 ± 2.5% fall
in
contralateral arm volume (P = 0.091) (Table 1). The
arms of the patients who
did not develop BCRL changed
little in volume.
Lymph drainage rates 7
months after axillary surgery
Three findings emerged from studies
1–2.
(1) k in the muscle was consistently greater than in the
subcutis of
the same arm, exceeding subcutis k in 69/72
arms (P 0.0001, paired t test)
(Table 2; Fig. 1, panel
a). The ratio muscle k/subcutis k was 2.1 ± 0.9 in
the
ipsilateral arm and 2.2 ± 1.1 in the contralateral arm
(n = 36). The
absolute value of muscle k, 0.15%/min
(Table 2), showed that *9% of the
muscle interstitial
fluid is drained by the lymphatics and replaced by
capillary
ultrafiltrate per h. The entire interstitial fluid volume
of
muscle thus turns over in *11 h. The turnover time
for subcutis (k =
0.077%/min; Table 2) is much slower,
*22 h.
(2) Lymph drainage in the
subcutis and muscle of the
ipsilateral arm was the same as in the
contralateral arm
(n = 36) (Fig. 1, panel b). This indicated that surgery
had
not in general caused any chronic deterioration of peripheral
lymph
flow by 7 months. Similarly, in the 7 women
destined to develop BCRL, muscle
k in the ipsilateral arm
(0.171 ± 0.054%/min) was not significantly lower
than in
the contralateral arm (0.188 ± 0.089%/min, P = 0.72,
paired t
test), although the 15% lower k in the subcutis of
the ipsilateral arm
approached statistical significance
(P = 0.085) (Table 2).
(3)
Unexpectedly, the drainage rate constants were
higher in both the
ipsilateral and contralateral arms of the
BCRL-destined patients, with as
yet no oedema, than in the
non-BCRL subgroup (Fig. 2). The difference was
substantial
and was seen consistently in both the subcutis and
the
muscle, and in both the ipsilateral and the contralateral
arms (Table 2).
Ipsilateral and contralateral muscle k values
were, respectively 22 and 29%
higher in the BCRL
than in non-BCRL subgroup (P = 0.007; P = 0.4
for
comparison of arms, 2-way ANOVA). Similarly, ipsilateral
and
contralateral subcutis k values were 22 and 50% higher
Breast Cancer Res
Treat
123
in the pre-BCRL patients than in the non-BCRL subgroup
(P =
0.002; P = 0.4 for arms).
Change in lymph drainage rates in the BCRL
subgroup
from 7 to 30 months
Seven women developed mild ipsilateral BCRL
by 30
months. Consistent with previous work [15, 16], subcutis k
fell by
*18% in the lymphoedematous arm relative to its
value at 7 months (Fig. 3,
panel a). Contrary to expectation,
subcutis k declined also in the
contralateral arm of the
BCRL patients. As a result the subcutis k was only
slightly
lower in the lymphoedematous arm than in the opposite
arm (P =
0.67 for difference between arms) (Table 2).
Two-way ANOVA showed that the
fall in k with time was
statistically significant (P = 0.020) while the
difference
between arms was not (P = 0.45). The deterioration in
subcutis
k (the difference between k at 7 and 30 months)
did not correlate with
patient age.
Muscle k showed no significant difference between the
two
arms at 30 months (P = 0.75) (Table 2). In contrast
with the deterioration
in subcutis k over time, muscle k did
not fall between 7 and 30 months (Fig.
3, panel b). Instead
it tended to increase in both arms, although this did
not
reach conventional significance (P = 0.11, 2-way
ANOVA). The
magnitude of the changes in muscle or
subcutis k did not correlate
significantly with the magnitude
of the swelling. Since subcutis k fell
while muscle k
increased, the subcutis/muscle ratio fell markedly,
namely
by 34% in the lymphoedematous arm, from 0.57 ± 0.24
at 7 months to
0.35 ± 0.17 at 30 months (P = 0.016,
Wilcoxon test) (Fig. 4, left panel). In
the contralateral arm
the ratio fell by 28%, from 0.68 ± 0.39 at 7 months
to
0.39 ± 0.12 at 30 months (P = 0.047).
Table 1 Arm volumes (ml)
following axillary surgery (mean ± SD)
Subgroup (n) 7 months 30
months
Ipsilateral Contralateral Pa Ipsilateral Contralateral Pa
All
cases (36) 1,917 ± 360 1,906 ± 377 0.34 – – –
BCRL (7) 1,935 ± 367b 1,893 ± 325 0.081 1,958 ± 347 1,851 ± 320 0.001
Non-BCRLc 1,913 ± 365 1,909 ± 394
0.79 1,895 ± 375 1,899 ± 361 0.81
Lymphoedema was absent at 7 months but had
developed in the ipsilateral arms of the BCRL subgroup by
30
months
a Ipsilateral versus contralateral arms, paired t test
b 2.0%
bigger than the contralateral arm (5/7 arms were on the dominant side)
c n =
29 at 7 months, n = 26 at 30 months; for the 25 women who completed all 4
studies to 30 months, at
7 months ipsilateral arm volume
was
1,915 ± 377 ml and contralateral arm volume was 1,916 ± 409 ml
Table 2 Arm
lymph drainage rates, represented by the removal rate constant for 99mTc-HIG
(k, %/min), at
7 and 30 months post-axillary
surgery (mean ± SD,
negative sign of k omitted)
7 months 30 months
Ipsilateral Contralateral
Pa Ipsilateral Contralateral Pa
All cases (n = 36)
Subcutis 0.077 ± 0.023
0.077 ± 0.028 0.93 – – –
Muscle 0.147 ± 0.032 0.154 ± 0.055 0.48 – – –
Pb
\0.0001 \0.0001 – – –
BCRL subgroup (n = 7)
Subcutis 0.090 ± 0.026 0.106
± 0.036 0.085 0.074 ± 0.031 0.078 ± 0.017 0.67
Muscle 0.171 ± 0.054 0.188 ±
0.089 0.72 0.227 ± 0.082 0.215 ± 0.055 0.75
Non-BCRL subgroupc
Subcutis
0.074 ± 0.021 0.070 ± 0.021 0.32 0.083 ± 0.030 0.083 ± 0.029 0.91
Muscle
0.141 ± 0.022 0.146 ± 0.041 0.50 0.170 ± 0.044 0.180 ± 0.041 0.18
a
Ipsilateral versus contralateral arms
b Subcutis versus muscle, paired t
tests
c n = 29 at 7 months, n = 26 (subcutis) and n = 25 (muscle) at 30
months; for the 25 women who
completed all 4 studies to 30
months,
at 7 months subcutis k was—ipsilateral: 0.074 ± 0.022%/min,
contralateral: 0.072 ± 0.022%/min, and
muscle k
was—ipsilateral:
0.140 ± 0.023%/min, contralateral: 0.143 ±
0.042%/min
Breast Cancer Res Treat
123
Change in lymph drainage rates
in the non-BCRL
subgroup from 7 to 30 months
In the 81% of women spared
of BCRL the pattern of
change was different from that in the BCRL group, in
that k
increased in both the subcutis and muscle between
7 months and 30
months (Fig. 3, panel b). Subcutis k
increased by 18 ± 38% ipsilaterally and
16 ± 30% contralaterally
(n = 26, P = 0.048, 2-way ANOVA). Muscle
k
likewise increased, by 24 ± 37% ipsilaterally and
36 ± 47% contralaterally
(n = 25, P\0.0001). The arms
did not differ significantly (P C 0.3). These
changes
showed no correlation with age.
Since k increased in both the
subcutis and muscle, their
ratio changed little. In the ipsilateral arm the
mean ratio
was 0.54 ± 18 at 7 months and 0.54 ± 0.26 at 30 months
(n =
25, P = 0.78, Wilcoxon test). Contralaterally the
ratio was 0.52 ± 0.21 at 7
months and 0.49 ± 0.21 at
30 months (n = 25, P = 0.059) (Fig. 4, right
panel). This
contrasted markedly with the lymphoedematous arms, in
which
the subcutis/muscle ratio fell by 28–34% (Fig. 4, left
panel).
As at 7
months, muscle k in the BCRL group at
30 months exceeded that in the
non-BCRL group, by 34%
in the ipsilateral arm and 19% in the contralateral
arm
(n = 7 and 25, P = 0.002 for difference between groups,
2-way ANOVA)
(Table 2). Subcutis k in the BCRL group
at 30 months no longer exceeded that
in the non-BCRL
group because it had fallen
bilaterally.
Discussion
This study demonstrates that the traditional view
of BCRL
as an obstructive lymphoedema caused by axillary surgery
is too
simplistic. There was no deterioration in muscle or
Fig. 1 High muscle lymph
flow
and unimpaired ipsilateral
drainage rates (k) in 36
postoperative
patients without
BCRL at 7 months postsurgery.
a
Individual k values
from all ipsilateral and
contralateral arms, with
lines
connecting muscle and subcutis
k in same arm; muscle k was
2–3
times subcutis k (n = 72
arms, P\0.0001). b Individual
k values from the
muscle and
subcutis of each arm, with the
mean and SD (thick and
thin
horizontal lines, respectively);
k in the ipsilateral arm did
not
differ significantly from k in the
contralateral arm in
either
compartment (P-values, paired
t tests)
Fig. 2 High fluid
turnover rates in patients with latent BCRL at
7 months post-surgery. Lymph
drainage rate constants (k, mean ±
SEM) in the subcutis and muscle of both
arms were higher in the
women destined to develop BCRL in *12 months time
(pre-BCRL,
n = 7) (open columns) than in the women would not develop
BCRL
(non-BCRL, n = 25–29, P\0.01, 2-way ANOVA)
(shaded
columns)
Breast Cancer Res Treat
123
subcutis lymph flow at
7 months, in either the entire group
or the subgroup that progressed to
BCRL. There was
therefore no support for the hypothesis of muscle
lymphatic
impairment during the pre-oedema phase. Muscle
lymph flow at 7
months was actually higher in both arms of
women who progressed to BCRL than
in those who did
not. Since lymph production is coupled closely to
capillary
filtration (k reflects lymph production as well as flow), it
is
likely that the women who progress to BCRL have greater
filtration
into the arm that overwhelms vulnerable lymphatics.
We propose therefore
that the first abnormality to
develop in the pathogenesis of BCRL is not
lymphatic
obstruction but high fluid filtration into both arms
with
subsequent lymphatic failure and the development
of
oedema.
Incidence of BCRL and risk factors
The incidence of BCRL
following standard axillary nodal
surgery (19% at 7–30 months, 32.5%
including the incipient
cases) is consistent with previous studies [2–5].
The
reported frequency of BCRL among women treated for
breast cancer
varies because of differing definitions of
BCRL and differing follow-up
periods. In the present study
arms were examined using strict clinical
criteria for
oedema and diagnosis was not based on arbitrary
circumference
or volume thresholds that may not detect mild
cases [20].
Approximately 75% of cases of BCRL develop
within 2 years of treatment and
90% within 3 years [23], so
most expected cases from the original cohort of
43 were
manifest. The BCRL group differed from the non-BCRL
group
somewhat, in particular the fewer lymph nodes
removed, which might have been
expected to reduce the
risk of BCRL, with statistically weaker differences
in age
and size of breast tumour.
Fig. 3 Changes in lymph removal rate
constant (k) from 7 to
30 months post-surgery (mean ± SEM; filled symbols,
muscle k;
open symbols, subcutis k). a The BCRL group developed
ipsilateral
lymphoedema by 30 months. The ipsilateral arm showed a fall
in
subcutis k but not muscle k, with similar changes in the
contralateral
arm. b Women who did not develop BCRL (non-BCRL
group)
showed a bilateral rise in subcutis and muscle k, similar to
the
bilateral increase in muscle k in the BCRL patients. The
distinguishing
feature of the BCRL group was thus a bilateral fall in
subcutis k
Fig. 4 Ratio of lymph removal rate constant in subcutis to that
in
muscle (ksubcutis/kmuscle, mean ± SEM) for the ipsilateral and
contralateral
arms of women who develop BCRL (left panel, filled
symbols)
and for those who do not develop BCRL (right panel, open
symbols)
at 7 and 30 months post-surgery. ksubcutis/kmuscle decreased in
both
arms of the BCRL group from 7 to 30 months (n = 7, P\0.05,
Wilcoxon
test) whereas changes in the non-BCRL group were small.
Logarithmic ordinate
to normalise ratio distribution
Breast Cancer Res Treat
123
Muscle
versus subcutis fluid turnover
Muscle k was consistently*2–3 times higher
than subcutis
k in the same arm, in agreement with earlier
indications
from separate patient groups [14, 15]. This indicates
that
interstitial fluid drainage into the microlymphatic system is
2–3
times faster in muscle than subcutis. Since the rate of
lymph and
interstitial fluid formation is closely coupled to
capillary filtration rate
in the steady state [24, 25], the
findings indicate a faster generation of
interstitial fluid by
capillary filtration in muscle. While differences in
the
Starling forces may contribute to this, the most obvious
explanation
is that the numerical density of blood capillaries
in skeletal muscle
(300–1,000/mm2) is *3 times that
in adipose subcutis [26–28]. The difference
in k and the
greater mass of muscle indicates that the subfascial
compartment
generates most of the lymphatic ‘load’ (volume
per unit time)
reaching the axilla.
High-filtering patients susceptible to
lymphoedema
At 7 months the peripheral lymph flow in the muscle
and
subcutis of both arms was significantly higher in the pre-
BCRL women
than the non-BCRL women (Fig. 2). Muscle
lymph flow was likewise higher in
the BCRL women than
controls at 30 months (Table 2). The coupling of
lymph
flow and capillary filtration rate (Jv) leads us to infer
the
existence of a subgroup of ‘high-filtering’ breast cancer
patients at
increased risk of BCRL.
There are two possible mechanisms whereby a
higher
lymph load might contribute to the onset of lymphoedema.
First,
lymph transport by lymphatic trunk vessels involves
an active contractile
process and is subject to overload
failure [24, 29]. The high volume load
discovered here may
therefore be a factor leading to eventual chronic
failure.
Second, if lymphatic contractility decreases for any reason,
the
consequences for tissue fluid balance will be worst in
individuals that
present the greatest volume of lymph for
transport.
Direct evidence for a
constitutively raised Jv in BCRL is
lacking, but earlier QL findings from
hand subcutis in
BCRL patients with and without hand swelling are
compatible
with this. In women with swelling involving the
hand, lymph
flow in the contralateral, unaffected hand was
higher than in the swollen
hand and higher than in either
hand of women without hand involvement [17].
This is
compatible with a constitutive higher filtration state in
more
severely affected patients. Furthermore, the contralateral
dermal
microlymphatics of BCRL patients are wider
than in non-BCRL breast cancer
patients, pointing again to
a constitutive difference [30]. Jv has been
measured for the
whole forearm (skin, subcutis and muscle) by
venous
occlusion plethysmography and was similar in the swollen
and
contralateral arms in long-established BCRL [31]; Jv
has not been measured
in the latent phase in pre-BCRL
patients relative to non-BCRL
patients.
What factor(s) might raise Jv? Decreased tone of
resistance
vessels would increase capillary pressure and hence
Jv, but no
impairment of sympathetic vasoconstrictor or
vasodilator control was
detected in BCRL [32]. Angiogenesis
could raise blood flow, capillary
surface area and
filtration rate, but there has been no comparison of
these
parameters between latent pre-BCRL patients and non-
BCRL patients.
The total number of capillaries increases in
the expanded skin of the
lymphoedematous arm, which
would increase fluid turnover [33, 34].
A
working hypothesis
The new results, combined with those from studies
at
92–97 months post-surgery [14, 15], provide a novel,
reasonably
complete natural history of BCRL (Fig. 5). Both
arms of the
BCRL patients evinced a fall in subcutis k in
association with mild, early
lymphoedema. Since k deteriorated
bilaterally, it appears to be constitutive
in nature, or
possibly a systemic effect of cancer treatment. The
absence
of deterioration in muscle k at this time may be due to
early,
mild nature of the lymphoedema (muscle k is markedly
depressed in
long-standing BCRL), and the rise in muscle k
contralaterally (Fig. 5) may
be the result of improvement in
health and physical exercise.
Previous QL
studies investigating more severe BCRL
(25–34% swelling) showed that both
subcutis and muscle k
eventually become markedly impaired in the swollen
arm
relative to the contralateral arm, the deterioration being
greater in
muscle [14, 15] (Fig. 5). This appears to offer a
rational explanation for
the severe oedema. Early, mild
swelling was associated with a bilateral fall
in subcutis k,
while the more severe, late swelling was associated with
a
large fall in muscle k. The lower k values in severe swelling
indicate
a relative stagnation of the interstitial fluid, its
turnover time rising to
18 h in muscle (cf. 11 h at
7 months) and 24 h in subcutis. In the present,
mild cases,
where there was no clear difference in k between the
two
arms, the oedema may have formed on the treated side due
to upstream
pump failure between 7 and 30 months, and a
constitutive, bilateral fall in
fluid turnover may have
obscured a small difference between arms.
We
propose the following working hypothesis. The primary
surgical injury to the
lymph nodes increases the
resistance to lymph flow in all women [35]. In
high-filtering
women with a high lymphatic load, the chronically
raised
afterload eventually impairs lymphatic smooth muscle
contractility
[29]. Just as in heart failure, the ‘backward
failure’ of the lymphatic pump
raises the lymphatic filling
pressure, i.e. interstitial fluid pressure [36,
37]. This can
Breast Cancer Res Treat
123
help to preserve lymph flow
and reduce capillary filtration
rate to match the reduced lymph flow [24].
In this way a
steady state is reached at an increased limb
volume,
increased interstitial pressure, and a relatively modest fall
in
lymph flow.
Conclusion
The finding of high lymph flows in the
muscle and subcutis
of both arms of pre-BCRL women leads to the
novel
hypothesis that patients with constitutively elevated
peripheral
lymph flows, and by implication capillary filtration
rates, form a subgroup
predisposed to BCRL after
surgery. This could explain why BCRL can develop
in
women who have had relatively few lymph nodes removed,
and raises the
possibility of predictive testing for BCRL
susceptibility. Support for this
hypothesis would come
from a prospective study of breast cancer patients
from
before surgery until such time as BCRL might
develop.
Acknowledgments We thank the patients, Mr G. Querci della
Rovere
(Royal Marsden Hospital, Sutton), Mr A.K. Sharma (St
George’s Hospital,
London) for access to the patients; Dr R. Allan
(St George’s Hospital) for
holding the ARSAC certificate; A. Irwin
(St George’s Hospital) for physics
support; and J. Ballinger (Guy’s
Hospital, London) and M. Wilkinson (St
George’s Hospital) for
radiopharmacy support. Grant support: We thank the
Wellcome
Trust (grant number 063025 awarded to P.S. Mortimer) and
the
Frances and Augustus Newman Foundation (equipment
grant).
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Breast Cancer Res Treat
123
STUDY
Lymphatic drainage in the muscle and subcutis of the arm
after
breast cancer treatment
Anthony W. B. Stanton Æ Stephanie Modi Æ
Thomas
M. Bennett Britton Æ Anand D. Purushotham Æ
A. Michael Peters Æ J. Rodney
Levick Æ Peter S. Mortimer
Received: 5 September 2008 / Accepted: 17
November 2008
Springer Science+Business Media, LLC. 2008
Abstract Breast
cancer-related lymphoedema of the arm
(BCRL) results from impaired lymph
drainage after axillary
surgery. Little is known about lymphatic changes
in
the arm between surgery and oedema onset. We measured
forearm muscle
and subcutis lymph drainage in 36 women
at 7 and 30 months after surgery by
quantitative lymphoscintigraphy.
None had BCRL initially but 19% had
BCRL
by 30 months. At 7 months muscle and subcutis drainage
in both arms
of BCRL-destined women exceeded that of
non-BCRL women (P\0.01). Muscle
lymph drainage
always exceeded subcutis drainage (P\0.0001). Muscle
lymph
drainage in the ipsilateral arm was unimpaired relative
to the contralateral
arm. BCRL therefore developed in
women with higher peripheral lymph flows.
The major
lymphatic load was generated by muscle; there was no pre-
BCRL
lymphatic impairment in the muscle of the ipsilateral
arm. We propose that
some women have a defined,
constitutive predisposition to secondary
lymphoedema.
Specifically, women with higher filtration rates,
and
therefore higher lymph flows through the axilla that are
closer to
the maximum sustainable, are at greater risk of
BCRL following axillary
trauma, even following removal
of 1–2 nodes.
Keywords Arm Breast cancer
Lymphatic
Lymphoedema Lymphoscintigraphy Lymph
flow
Introduction
Axillary nodal surgery and radiotherapy for breast
cancer
interfere with lymph drainage from the ipsilateral arm. In
21–33%
of women this results in a swelling of the arm,
breast cancer-related
lymphoedema (BCRL), after a delay
of months to years [1–5]. BCRL is
associated with pain,
impaired function, psychological morbidity,
cellulitis,
occasionally skin malignancy, and remains a
significant
clinical problem. There is a perception that the
introduction
of breast-conserving surgery, and sentinel lymph node
biopsy
(SLNB) in particular, has made BCRL a thing of the
past but the evidence
does not support this. After SLNB
alone the incidence is 5–7% [6–8] but the
incidence is
almost certainly higher in patients in whom more than
one
axillary node is removed or in whom a double procedure
(positive SLNB
followed by axillary clearance) is
performed.
A. W. B. Stanton (&)
S. Modi P. S. Mortimer
Cardiac & Vascular Sciences (Dermatology), St
George’s
Hospital Medical School, University of London,
Cranmer Terrace,
London SW17 0RE, UK
e-mail: [email protected]
T. M. Bennett
Britton
Cambridge Breast Unit, Addenbrooke’s Hospital,
Cambridge CB2 2QQ,
UK
A. D. Purushotham
Hedley Atkins Breast Unit, Academic
Oncology,
Guy’s and St Thomas’ Trust, London SE1 9RT, UK
A. D.
Purushotham
King’s College London, London WC2R 2LS, UK
A. M.
Peters
Nuclear Medicine, Royal Sussex County Hospital,
Brighton BN2 5BE,
UK
J. R. Levick
Basic Medical Sciences (Physiology), St George’s
Hospital
Medical School, University of London, London SW17 0RE, UK
P. S.
Mortimer
Skin and Rare Cancers, Royal Marsden Hospital,
Sutton SM2 5PT,
UK
123
Breast Cancer Res Treat
DOI 10.1007/s10549-008-0259-z
The
understanding of the pathophysiology of BCRL was
limited by technical
difficulties in assessing human
lymphatic function. In long-established
lymphoedema,
radiocontrast lymphangiography demonstrated dilated
and
tortuous lymphatics, dermal backflow and extravasation of
contrast
medium [9]. These changes were attributed to
axillary obstruction because
the epifascial vessels (draining
skin and subcutis) run mainly to the
axilla, although some
also anastomose with a scapular collateral pathway
[10],
and the subfascial (muscle) vessels drain exclusively to
the
axilla. The epifascial and subfascial compartments communicate
at the
wrist and elbow [10, 11]. Most swelling is
epifascial, particularly in the
highly compliant subcutis
[12, 13]. Subfascially, swelling is limited by the
tight
enveloping fascia, but the volume of fluid presented to
the
lymphatics each minute may be higher than in the subcutis
due to the
higher density of filtering capillaries in skeletal
muscle. Supporting this
view, estimated lymph flow from
muscle [14] exceeds that from subcutis
[15–17].
Peripheral lymph flow is assessed best by
quantitative
lymphoscintigraphy (QL) in which the fractional
removal
rate, k, of an injected radiolabelled macromolecule is
measured,
representing local lymph drainage rate per unit
volume of tissue fluid [18].
In the subcutis of the swollen
forearm, local lymph drainage is markedly
reduced relative
to the contralateral arm [15, 16]. Lymph drainage is
also
reduced in the forearm muscle, by 31% in arms with 33%
swelling
[14]. There is a graded relation between reduction
in muscle lymph drainage
and severity of the swelling, but
not between reduction in subcutis lymph
drainage and
swelling [14–16]. Lymphatic function in muscle and
subcutis
has not to date been compared in the same patients,
and little
is known of lymphatic function before overt
oedema. Investigation of the
hand subcutis 3 months after
axillary surgery (with no oedema) showed no
local
impairment of lymph drainage [19]. Declining muscle
lymphatic
function may be crucial to the pathogenesis of
BCRL, and we considered that
muscle lymphatic failure
might precede onset of oedema. We therefore
measured
lymph flow in the forearm muscle and subcutis of women
treated
recently by axillary surgery, initially without
BCRL, and repeated the
measurements 2 years later by
which time some had developed
BCRL.
Patients and methods
Patients and assessment of arms
Forty-three
breast cancer patients from St George’s
Hospital, London, the Royal Marsden
Hospital, Sutton,
and Addenbrooke’s Hospital, Cambridge, were
assessed
7.3 ± 2.8 months (mean ± SD) after surgery. Seven of the
43
(16%) were found to have signs of (previously undiagnosed)
incipient arm
oedema (see below) and were
therefore excluded, leaving 36 women aged 61 ± 9
years
(range: 46–81 years) of body mass index (BMI) 25.9 ±
3.8 kg/m2
without detectable BCRL for this study. All
patients had undergone standard
axillary nodal surgery
(mainly level I ? II); none received axillary
radiotherapy.
No patient had other serious disease or was on
Ca2?-
channel blockers or developed cancer recurrence during the
study.
All were right-handed.
The diagnosis of BCRL in the excluded patients and
in
the patients who later developed BCRL was based on
examination for the
clinical signs of oedema, rather than
arm volume alone [20]. BCRL was
considered to be
present in the ipsilateral arm if (1) the subcutaneous
veins
of the ventral forearm and dorsal hand were less visible
than on
the contralateral side; (2) there was a rounding or
fullness in the medial
elbow and distal upper arm regions;
(3) skin and subcutis thickness was
increased; (4) pitting
oedema was present. Arm volumes were measured using
a
Perometer 350S limb volumeter (Pero-System, Wuppertal,
Germany) in 26
patients, and a tape-measure (with calculation
of arm volume from serial
circumferences measured
at 4 cm intervals) in the remaining 10 [21]. The
eventual 7
BCRL patients had had significantly fewer axillary lymph
nodes
excised than the 29 non-BCRL patients (8 ± 3 vs.
15 ± 8, P = 0.032, unpaired
t test); the BCRL group was
6 years younger than the non-BCRL group (57.1 ±
3.3 vs.
63.2 ± 9.2 years at 7 months post-surgery, P = 0.10), had
smaller
primary tumours (17 ± 7 vs. 23 ± 10 mm,
P = 0.13), and had received a
smaller proportion of mastectomies
(14 vs. 21%) as opposed to wide local
excisions.
Every BCRL patient and 21/29 non-BCRL patients
received
breast/chest wall radiotherapy, which may
increase the risk of BCRL [5]. The
BMI of the BCRL and
the non-BCRL groups was almost identical (P =
0.77).
The study was approved by the Research Ethics
Committees,
conformed to the Declaration of Helsinki, and was
approved by
the Administration of Radioactive Substances
Advisory Committee, UK (ARSAC).
The effective radiation
dose was *0.04 mSv per patient. All
participants
gave informed, written consent.
Quantitative
lymphoscintigraphy and time course
of studies
QL was performed on the
forearm in order to measure k
(local lymph flow/volume of distribution of
tracer). The
radiopharmaceutical was human IgG (TechneScan HIG,
DRN 4369;
Mallinckrodt, Petten, Netherlands) labelled with
99mTc (99mTc-HIG).
Radiochemical purity was 99.1%. The
scintillation detectors (Ametek,
Wokingham, UK) were
calibrated for the pulse energy of 99mTc (137–143 keV).
QL
Breast Cancer Res Treat
123
and the theory equating k to lymph
drainage have been
described in detail and reviewed critically [14–18, 22].
The
patients underwent 4 bilateral QL studies; study 1 (at 7.3
months
post-surgery): k in the subcutis, study 2 (within
7 days of study 1): k in
the muscle, studies 3 and 4 (at 30.5 ±
4.0 months): repetition of studies 1
and 2. At 30 months the
arms were assessed again for clinical signs of
oedema.
After 45 min acclimatisation at 23 ± 1C the forearms
were
supported at heart level and an injection point marked
on each ventral
forearm at 390 ± 20 mm from the middle
fingertip and 60 ± 10 mmlateral to
the midline. 99mTc-HIG
(0.2 ml, 0.60 ± 0.08 MBq) was injected
subcutaneously
for studies 1 and 3 or intramuscularly for studies 2 and
4.
The scintillation detectors were positioned *1 mm above
the skin over
each depot. The maximum depot diameter,
31 mm, was\50% of the diameter of
the skin area under the
detector (65 mm) [15]. Acquisitions (duration 100s)
were
performed every 15 min for 3 h. During the intervening
periods the
patient mostly sat but was also allowed to walk
short distances. The arms
and detectors were carefully
repositioned for each
acquisition.
Calculation of k
Counts were corrected for background and
radioactive
decay, according to N = N0e-ct (N corrected counts,
N0
uncorrected counts, c decay constant (0.001923/min), t min
since
injection). The counts remaining in the depot were then
expressed as the
fraction of the counts from the first acquisition,
and the slope of the loge
of the fraction versus time
plot (9100) gave the percentage of the depot
cleared per
minute, k (%/min). The slope was measured from the end of
any
initial lag phase (28–30% of cases, duration*30 min).
Statistical
analysis
Results are shown as the mean ± standard deviation (SD),
with the
range for some results, and the standard error of the
mean (SEM) in the
figures. Groups were compared using
Student’s unpaired and paired t tests,
Wilcoxon’s matched
pairs test for non-Gaussian ratios of subcutis k to
muscle k,
and 2-way analysis of variance (ANOVA). The slope of the
depot
clearance plot was obtained by linear regression.
Analysis was performed
using Prism 4.0 (GraphPad, San
Diego, CA). Significance was accepted at
P\0.05.
Results
Compliance, incidence of BCRL and arm
volumes
Thirty-six women completed studies 1–2, 33 completed
studies 1–3
and 32 completed studies 1–4. Arm volumes at
7 months for the whole group
were similar on the ipsilateral
and contralateral sides (n = 36) (Table 1).
Six patients
were diagnosed with BCRL at 19 ± 5 months (11–23
months)
after surgery. One further patient was found to
have previously unrecognised
clinical signs of oedema at
study 3, giving an overall incidence of BCRL
from 7 to
30 months of 19%. Including the rejected incipient cases,
the
incidence (from 2 months) was 14/43 (32.5%).
At 30 months the
lymphoedematous arm was 5.8 ± 2.0%
bigger than the contralateral arm (n = 7,
P = 0.0007, paired
t test) (Table 1). The difference in arm volume was
due
partly to ipsilateral swelling and partly to a 2.2 ± 2.5% fall
in
contralateral arm volume (P = 0.091) (Table 1). The
arms of the patients who
did not develop BCRL changed
little in volume.
Lymph drainage rates 7
months after axillary surgery
Three findings emerged from studies
1–2.
(1) k in the muscle was consistently greater than in the
subcutis of
the same arm, exceeding subcutis k in 69/72
arms (P 0.0001, paired t test)
(Table 2; Fig. 1, panel
a). The ratio muscle k/subcutis k was 2.1 ± 0.9 in
the
ipsilateral arm and 2.2 ± 1.1 in the contralateral arm
(n = 36). The
absolute value of muscle k, 0.15%/min
(Table 2), showed that *9% of the
muscle interstitial
fluid is drained by the lymphatics and replaced by
capillary
ultrafiltrate per h. The entire interstitial fluid volume
of
muscle thus turns over in *11 h. The turnover time
for subcutis (k =
0.077%/min; Table 2) is much slower,
*22 h.
(2) Lymph drainage in the
subcutis and muscle of the
ipsilateral arm was the same as in the
contralateral arm
(n = 36) (Fig. 1, panel b). This indicated that surgery
had
not in general caused any chronic deterioration of peripheral
lymph
flow by 7 months. Similarly, in the 7 women
destined to develop BCRL, muscle
k in the ipsilateral arm
(0.171 ± 0.054%/min) was not significantly lower
than in
the contralateral arm (0.188 ± 0.089%/min, P = 0.72,
paired t
test), although the 15% lower k in the subcutis of
the ipsilateral arm
approached statistical significance
(P = 0.085) (Table 2).
(3)
Unexpectedly, the drainage rate constants were
higher in both the
ipsilateral and contralateral arms of the
BCRL-destined patients, with as
yet no oedema, than in the
non-BCRL subgroup (Fig. 2). The difference was
substantial
and was seen consistently in both the subcutis and
the
muscle, and in both the ipsilateral and the contralateral
arms (Table 2).
Ipsilateral and contralateral muscle k values
were, respectively 22 and 29%
higher in the BCRL
than in non-BCRL subgroup (P = 0.007; P = 0.4
for
comparison of arms, 2-way ANOVA). Similarly, ipsilateral
and
contralateral subcutis k values were 22 and 50% higher
Breast Cancer Res
Treat
123
in the pre-BCRL patients than in the non-BCRL subgroup
(P =
0.002; P = 0.4 for arms).
Change in lymph drainage rates in the BCRL
subgroup
from 7 to 30 months
Seven women developed mild ipsilateral BCRL
by 30
months. Consistent with previous work [15, 16], subcutis k
fell by
*18% in the lymphoedematous arm relative to its
value at 7 months (Fig. 3,
panel a). Contrary to expectation,
subcutis k declined also in the
contralateral arm of the
BCRL patients. As a result the subcutis k was only
slightly
lower in the lymphoedematous arm than in the opposite
arm (P =
0.67 for difference between arms) (Table 2).
Two-way ANOVA showed that the
fall in k with time was
statistically significant (P = 0.020) while the
difference
between arms was not (P = 0.45). The deterioration in
subcutis
k (the difference between k at 7 and 30 months)
did not correlate with
patient age.
Muscle k showed no significant difference between the
two
arms at 30 months (P = 0.75) (Table 2). In contrast
with the deterioration
in subcutis k over time, muscle k did
not fall between 7 and 30 months (Fig.
3, panel b). Instead
it tended to increase in both arms, although this did
not
reach conventional significance (P = 0.11, 2-way
ANOVA). The
magnitude of the changes in muscle or
subcutis k did not correlate
significantly with the magnitude
of the swelling. Since subcutis k fell
while muscle k
increased, the subcutis/muscle ratio fell markedly,
namely
by 34% in the lymphoedematous arm, from 0.57 ± 0.24
at 7 months to
0.35 ± 0.17 at 30 months (P = 0.016,
Wilcoxon test) (Fig. 4, left panel). In
the contralateral arm
the ratio fell by 28%, from 0.68 ± 0.39 at 7 months
to
0.39 ± 0.12 at 30 months (P = 0.047).
Table 1 Arm volumes (ml)
following axillary surgery (mean ± SD)
Subgroup (n) 7 months 30
months
Ipsilateral Contralateral Pa Ipsilateral Contralateral Pa
All
cases (36) 1,917 ± 360 1,906 ± 377 0.34 – – –
BCRL (7) 1,935 ± 367b 1,893 ± 325 0.081 1,958 ± 347 1,851 ± 320 0.001
Non-BCRLc 1,913 ± 365 1,909 ± 394
0.79 1,895 ± 375 1,899 ± 361 0.81
Lymphoedema was absent at 7 months but had
developed in the ipsilateral arms of the BCRL subgroup by
30
months
a Ipsilateral versus contralateral arms, paired t test
b 2.0%
bigger than the contralateral arm (5/7 arms were on the dominant side)
c n =
29 at 7 months, n = 26 at 30 months; for the 25 women who completed all 4
studies to 30 months, at
7 months ipsilateral arm volume
was
1,915 ± 377 ml and contralateral arm volume was 1,916 ± 409 ml
Table 2 Arm
lymph drainage rates, represented by the removal rate constant for 99mTc-HIG
(k, %/min), at
7 and 30 months post-axillary
surgery (mean ± SD,
negative sign of k omitted)
7 months 30 months
Ipsilateral Contralateral
Pa Ipsilateral Contralateral Pa
All cases (n = 36)
Subcutis 0.077 ± 0.023
0.077 ± 0.028 0.93 – – –
Muscle 0.147 ± 0.032 0.154 ± 0.055 0.48 – – –
Pb
\0.0001 \0.0001 – – –
BCRL subgroup (n = 7)
Subcutis 0.090 ± 0.026 0.106
± 0.036 0.085 0.074 ± 0.031 0.078 ± 0.017 0.67
Muscle 0.171 ± 0.054 0.188 ±
0.089 0.72 0.227 ± 0.082 0.215 ± 0.055 0.75
Non-BCRL subgroupc
Subcutis
0.074 ± 0.021 0.070 ± 0.021 0.32 0.083 ± 0.030 0.083 ± 0.029 0.91
Muscle
0.141 ± 0.022 0.146 ± 0.041 0.50 0.170 ± 0.044 0.180 ± 0.041 0.18
a
Ipsilateral versus contralateral arms
b Subcutis versus muscle, paired t
tests
c n = 29 at 7 months, n = 26 (subcutis) and n = 25 (muscle) at 30
months; for the 25 women who
completed all 4 studies to 30
months,
at 7 months subcutis k was—ipsilateral: 0.074 ± 0.022%/min,
contralateral: 0.072 ± 0.022%/min, and
muscle k
was—ipsilateral:
0.140 ± 0.023%/min, contralateral: 0.143 ±
0.042%/min
Breast Cancer Res Treat
123
Change in lymph drainage rates
in the non-BCRL
subgroup from 7 to 30 months
In the 81% of women spared
of BCRL the pattern of
change was different from that in the BCRL group, in
that k
increased in both the subcutis and muscle between
7 months and 30
months (Fig. 3, panel b). Subcutis k
increased by 18 ± 38% ipsilaterally and
16 ± 30% contralaterally
(n = 26, P = 0.048, 2-way ANOVA). Muscle
k
likewise increased, by 24 ± 37% ipsilaterally and
36 ± 47% contralaterally
(n = 25, P\0.0001). The arms
did not differ significantly (P C 0.3). These
changes
showed no correlation with age.
Since k increased in both the
subcutis and muscle, their
ratio changed little. In the ipsilateral arm the
mean ratio
was 0.54 ± 18 at 7 months and 0.54 ± 0.26 at 30 months
(n =
25, P = 0.78, Wilcoxon test). Contralaterally the
ratio was 0.52 ± 0.21 at 7
months and 0.49 ± 0.21 at
30 months (n = 25, P = 0.059) (Fig. 4, right
panel). This
contrasted markedly with the lymphoedematous arms, in
which
the subcutis/muscle ratio fell by 28–34% (Fig. 4, left
panel).
As at 7
months, muscle k in the BCRL group at
30 months exceeded that in the
non-BCRL group, by 34%
in the ipsilateral arm and 19% in the contralateral
arm
(n = 7 and 25, P = 0.002 for difference between groups,
2-way ANOVA)
(Table 2). Subcutis k in the BCRL group
at 30 months no longer exceeded that
in the non-BCRL
group because it had fallen
bilaterally.
Discussion
This study demonstrates that the traditional view
of BCRL
as an obstructive lymphoedema caused by axillary surgery
is too
simplistic. There was no deterioration in muscle or
Fig. 1 High muscle lymph
flow
and unimpaired ipsilateral
drainage rates (k) in 36
postoperative
patients without
BCRL at 7 months postsurgery.
a
Individual k values
from all ipsilateral and
contralateral arms, with
lines
connecting muscle and subcutis
k in same arm; muscle k was
2–3
times subcutis k (n = 72
arms, P\0.0001). b Individual
k values from the
muscle and
subcutis of each arm, with the
mean and SD (thick and
thin
horizontal lines, respectively);
k in the ipsilateral arm did
not
differ significantly from k in the
contralateral arm in
either
compartment (P-values, paired
t tests)
Fig. 2 High fluid
turnover rates in patients with latent BCRL at
7 months post-surgery. Lymph
drainage rate constants (k, mean ±
SEM) in the subcutis and muscle of both
arms were higher in the
women destined to develop BCRL in *12 months time
(pre-BCRL,
n = 7) (open columns) than in the women would not develop
BCRL
(non-BCRL, n = 25–29, P\0.01, 2-way ANOVA)
(shaded
columns)
Breast Cancer Res Treat
123
subcutis lymph flow at
7 months, in either the entire group
or the subgroup that progressed to
BCRL. There was
therefore no support for the hypothesis of muscle
lymphatic
impairment during the pre-oedema phase. Muscle
lymph flow at 7
months was actually higher in both arms of
women who progressed to BCRL than
in those who did
not. Since lymph production is coupled closely to
capillary
filtration (k reflects lymph production as well as flow), it
is
likely that the women who progress to BCRL have greater
filtration
into the arm that overwhelms vulnerable lymphatics.
We propose therefore
that the first abnormality to
develop in the pathogenesis of BCRL is not
lymphatic
obstruction but high fluid filtration into both arms
with
subsequent lymphatic failure and the development
of
oedema.
Incidence of BCRL and risk factors
The incidence of BCRL
following standard axillary nodal
surgery (19% at 7–30 months, 32.5%
including the incipient
cases) is consistent with previous studies [2–5].
The
reported frequency of BCRL among women treated for
breast cancer
varies because of differing definitions of
BCRL and differing follow-up
periods. In the present study
arms were examined using strict clinical
criteria for
oedema and diagnosis was not based on arbitrary
circumference
or volume thresholds that may not detect mild
cases [20].
Approximately 75% of cases of BCRL develop
within 2 years of treatment and
90% within 3 years [23], so
most expected cases from the original cohort of
43 were
manifest. The BCRL group differed from the non-BCRL
group
somewhat, in particular the fewer lymph nodes
removed, which might have been
expected to reduce the
risk of BCRL, with statistically weaker differences
in age
and size of breast tumour.
Fig. 3 Changes in lymph removal rate
constant (k) from 7 to
30 months post-surgery (mean ± SEM; filled symbols,
muscle k;
open symbols, subcutis k). a The BCRL group developed
ipsilateral
lymphoedema by 30 months. The ipsilateral arm showed a fall
in
subcutis k but not muscle k, with similar changes in the
contralateral
arm. b Women who did not develop BCRL (non-BCRL
group)
showed a bilateral rise in subcutis and muscle k, similar to
the
bilateral increase in muscle k in the BCRL patients. The
distinguishing
feature of the BCRL group was thus a bilateral fall in
subcutis k
Fig. 4 Ratio of lymph removal rate constant in subcutis to that
in
muscle (ksubcutis/kmuscle, mean ± SEM) for the ipsilateral and
contralateral
arms of women who develop BCRL (left panel, filled
symbols)
and for those who do not develop BCRL (right panel, open
symbols)
at 7 and 30 months post-surgery. ksubcutis/kmuscle decreased in
both
arms of the BCRL group from 7 to 30 months (n = 7, P\0.05,
Wilcoxon
test) whereas changes in the non-BCRL group were small.
Logarithmic ordinate
to normalise ratio distribution
Breast Cancer Res Treat
123
Muscle
versus subcutis fluid turnover
Muscle k was consistently*2–3 times higher
than subcutis
k in the same arm, in agreement with earlier
indications
from separate patient groups [14, 15]. This indicates
that
interstitial fluid drainage into the microlymphatic system is
2–3
times faster in muscle than subcutis. Since the rate of
lymph and
interstitial fluid formation is closely coupled to
capillary filtration rate
in the steady state [24, 25], the
findings indicate a faster generation of
interstitial fluid by
capillary filtration in muscle. While differences in
the
Starling forces may contribute to this, the most obvious
explanation
is that the numerical density of blood capillaries
in skeletal muscle
(300–1,000/mm2) is *3 times that
in adipose subcutis [26–28]. The difference
in k and the
greater mass of muscle indicates that the subfascial
compartment
generates most of the lymphatic ‘load’ (volume
per unit time)
reaching the axilla.
High-filtering patients susceptible to
lymphoedema
At 7 months the peripheral lymph flow in the muscle
and
subcutis of both arms was significantly higher in the pre-
BCRL women
than the non-BCRL women (Fig. 2). Muscle
lymph flow was likewise higher in
the BCRL women than
controls at 30 months (Table 2). The coupling of
lymph
flow and capillary filtration rate (Jv) leads us to infer
the
existence of a subgroup of ‘high-filtering’ breast cancer
patients at
increased risk of BCRL.
There are two possible mechanisms whereby a
higher
lymph load might contribute to the onset of lymphoedema.
First,
lymph transport by lymphatic trunk vessels involves
an active contractile
process and is subject to overload
failure [24, 29]. The high volume load
discovered here may
therefore be a factor leading to eventual chronic
failure.
Second, if lymphatic contractility decreases for any reason,
the
consequences for tissue fluid balance will be worst in
individuals that
present the greatest volume of lymph for
transport.
Direct evidence for a
constitutively raised Jv in BCRL is
lacking, but earlier QL findings from
hand subcutis in
BCRL patients with and without hand swelling are
compatible
with this. In women with swelling involving the
hand, lymph
flow in the contralateral, unaffected hand was
higher than in the swollen
hand and higher than in either
hand of women without hand involvement [17].
This is
compatible with a constitutive higher filtration state in
more
severely affected patients. Furthermore, the contralateral
dermal
microlymphatics of BCRL patients are wider
than in non-BCRL breast cancer
patients, pointing again to
a constitutive difference [30]. Jv has been
measured for the
whole forearm (skin, subcutis and muscle) by
venous
occlusion plethysmography and was similar in the swollen
and
contralateral arms in long-established BCRL [31]; Jv
has not been measured
in the latent phase in pre-BCRL
patients relative to non-BCRL
patients.
What factor(s) might raise Jv? Decreased tone of
resistance
vessels would increase capillary pressure and hence
Jv, but no
impairment of sympathetic vasoconstrictor or
vasodilator control was
detected in BCRL [32]. Angiogenesis
could raise blood flow, capillary
surface area and
filtration rate, but there has been no comparison of
these
parameters between latent pre-BCRL patients and non-
BCRL patients.
The total number of capillaries increases in
the expanded skin of the
lymphoedematous arm, which
would increase fluid turnover [33, 34].
A
working hypothesis
The new results, combined with those from studies
at
92–97 months post-surgery [14, 15], provide a novel,
reasonably
complete natural history of BCRL (Fig. 5). Both
arms of the
BCRL patients evinced a fall in subcutis k in
association with mild, early
lymphoedema. Since k deteriorated
bilaterally, it appears to be constitutive
in nature, or
possibly a systemic effect of cancer treatment. The
absence
of deterioration in muscle k at this time may be due to
early,
mild nature of the lymphoedema (muscle k is markedly
depressed in
long-standing BCRL), and the rise in muscle k
contralaterally (Fig. 5) may
be the result of improvement in
health and physical exercise.
Previous QL
studies investigating more severe BCRL
(25–34% swelling) showed that both
subcutis and muscle k
eventually become markedly impaired in the swollen
arm
relative to the contralateral arm, the deterioration being
greater in
muscle [14, 15] (Fig. 5). This appears to offer a
rational explanation for
the severe oedema. Early, mild
swelling was associated with a bilateral fall
in subcutis k,
while the more severe, late swelling was associated with
a
large fall in muscle k. The lower k values in severe swelling
indicate
a relative stagnation of the interstitial fluid, its
turnover time rising to
18 h in muscle (cf. 11 h at
7 months) and 24 h in subcutis. In the present,
mild cases,
where there was no clear difference in k between the
two
arms, the oedema may have formed on the treated side due
to upstream
pump failure between 7 and 30 months, and a
constitutive, bilateral fall in
fluid turnover may have
obscured a small difference between arms.
We
propose the following working hypothesis. The primary
surgical injury to the
lymph nodes increases the
resistance to lymph flow in all women [35]. In
high-filtering
women with a high lymphatic load, the chronically
raised
afterload eventually impairs lymphatic smooth muscle
contractility
[29]. Just as in heart failure, the ‘backward
failure’ of the lymphatic pump
raises the lymphatic filling
pressure, i.e. interstitial fluid pressure [36,
37]. This can
Breast Cancer Res Treat
123
help to preserve lymph flow
and reduce capillary filtration
rate to match the reduced lymph flow [24].
In this way a
steady state is reached at an increased limb
volume,
increased interstitial pressure, and a relatively modest fall
in
lymph flow.
Conclusion
The finding of high lymph flows in the
muscle and subcutis
of both arms of pre-BCRL women leads to the
novel
hypothesis that patients with constitutively elevated
peripheral
lymph flows, and by implication capillary filtration
rates, form a subgroup
predisposed to BCRL after
surgery. This could explain why BCRL can develop
in
women who have had relatively few lymph nodes removed,
and raises the
possibility of predictive testing for BCRL
susceptibility. Support for this
hypothesis would come
from a prospective study of breast cancer patients
from
before surgery until such time as BCRL might
develop.
Acknowledgments We thank the patients, Mr G. Querci della
Rovere
(Royal Marsden Hospital, Sutton), Mr A.K. Sharma (St
George’s Hospital,
London) for access to the patients; Dr R. Allan
(St George’s Hospital) for
holding the ARSAC certificate; A. Irwin
(St George’s Hospital) for physics
support; and J. Ballinger (Guy’s
Hospital, London) and M. Wilkinson (St
George’s Hospital) for
radiopharmacy support. Grant support: We thank the
Wellcome
Trust (grant number 063025 awarded to P.S. Mortimer) and
the
Frances and Augustus Newman Foundation (equipment
grant).
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