Lymphedema represents potentially the most debilitating complication after any axillary surgery. Its true incidence can be difficult to determine, as no standardized definition of lymphedema exists. Volume displacement techniques are recognized as the gold standard in assessing lymphedema; however, this technique can be cumbersome in a busy clinical setting. Therefore, nearly all series2,3,5-17
have used circumferential measurements of the upper arm and forearm that act as a surrogate for volume change. The method of measurement, however, is not standardized, as various studies have reported arm measurement locations varying from 10 to 15 cm above the olecranon process, and from 5 to 15 cm below.3,5,11,16
Differences in measurement techniques make various studies difficult to compare.
Furthermore, defining lymphedema as a function of changes in upper-extremity circumference necessitates the availability of both baseline measurements and contralateral upper-extremity measurements. Although some groups have used the contralateral upper-extremity alone as a comparison to determine the presence of lymphedema, this method has its shortcomings. Significant differences in circumference may exist between a woman's dominant and nondominant upper extremities. Although in most women, these differences are less than 2 cm,18
a preexisting difference in the two upper-extremity circumferences could mask the detection of subsequent lymphedema in the smaller extremity. However, contralateral upper-extremity measurements are also essential. A significant change in body weight might increase the circumference of the ipsilateral upper extremity, resulting in an incorrect diagnosis of measured lymphedema if the upper-extremity measurement is only compared with the baseline measurement. Only by having comparison measurements from the contralateral upper extremity would one be able to distinguish an increase in body weight from the development of lymphedema. Thus baseline and contralateral upper-extremity measurements are essential to accurately determine a change in arm measurements and therefore the presence of lymphedema.
Two prospective randomized trials10,12
and several prospective nonrandomized series2,3,9,11,13,16,19
have concluded that lymphedema after SLNB is less common or severe than after ALND. Many of these studies do not report the actual incidence of lymphedema. Of those that do, the rates of lymphedema vary from 0% to 7% at 6 to 36 months after SLNB ().
Literature Reporting Measured Lymphedema After SLNB
The development of lymphedema is an unpredictable occurrence that can happen years after axillary surgery. Among those who develop lymphedema after ALND, the onset of symptoms occurs within 3 years in 77% of patients1
but after 3 years in approximately 25% of patients. Of women without lymphedema 3 years after ALND, the ongoing risk of developing lymphedema is approximately 1% per year for at least 20 years. With 20 years of follow-up, Petrek et al1
found lymphedema in 49% of patients, a significantly higher rate than the 6% to 30% usually reported after ALND. This suggests that the incidence of lymphedema is commonly underestimated as a result of the inadequate follow-up interval in most studies.
The development of lymphedema after SLNB is likely to follow the same pattern as for ALND. Therefore, only long follow-up will accurately predict its true incidence. Reported rates of lymphedema after SLNB of 0% to 7% with 6 to 36 months of follow-up likely represent only a fraction of patients who will ultimately be diagnosed with lymphedema. These rates are likely to increase as women are observed for longer periods of time. The current series reports the prevalence of lymphedema in women a median of 5 years postoperatively, thereby likely capturing the large majority of women who will develop lymphedema after SLNB.
It is difficult to compare our measured severe lymphedema rate of 0.5% with that of other series, as severe lymphedema after SLNB is rarely recorded or quantified as a measured value in the literature. Similar to the present study, Petrek et al1
defined severe lymphedema as a measured difference of more than 2 inches (5.08 cm). At 20 years, 13% of patients who underwent ALND were classified as having severe lymphedema. Sener et al19
defined postoperative arm volume differences of greater than 40% as severe lymphedema, but do not report its incidence. Others define it subjectively by patient report2,5,8,13
or as the need to wear a compression garment.20
To date, no series has reported severe lymphedema, as defined by arm measurements, in a patient after SLNB. However, as defined by patient report, Blanchard et al20
described the presence of subjective severe lymphedema after SLNB in four (0.6%) of 685 women, and Leidenius et al13
report it in one (1%) of 92 women. These values are similar to the observed 0.5% incidence of measured severe lymphedema in women who underwent SLNB in the present series.
In the current series, the risk factors that were significantly associated with the presence of lymphedema at a median of 5 years were greater body weight, higher BMI, infection, or injury. Obesity, increasing BMI, and weight gain are commonly recognized as risk factors for lymphedema.1,16,21
Although injury and infection have also been described as increasing the risk of lymphedema, the influence of these factors must be carefully examined. Both variables are dependent on patient recall. Although both seem to be significant risk factors, it is possible that women with lymphedema recall an inciting infection or injury more readily than a woman without lymphedema. Furthermore, it is possible that women with lymphedema are at higher risk of developing infection. Even injuries might be more commonly reported if women with lymphedema have greater difficulty recovering from injury, making it more memorable.
There are additional limitations of the current study. Because the patients were not randomly assigned to a treatment arm, the surgical procedure is almost entirely confounded by disease stage in this series. Also, as in nearly all other series, we used circumferential arm measurements, which, as opposed to volume displacement methods, will not detect those patients with isolated hand edema, therefore underestimating the incidence of lymphedema.
Circumferential arm measurements represent an objective method to determine the presence of lymphedema and cannot be influenced by sensory changes such as numbness or pain that are common after axillary surgery22
and can influence patient perceptions. However, measurements may not be the most reliable indicator of clinically significant lymphedema. An ipsilateral calculated measurement difference of more than 2 cm may be severely disfiguring in a thin woman and unnoticeable in an obese one. In addition, the influence of patient perceptions in the setting of lymphedema cannot be underestimated. It is likely that both objective upper-extremity measurements and symptom assessment are needed to determine the true prevalence of clinically significant lymphedema. We have reported our findings with regard to patient perceptions of lymphedema in an accompanying separate report.23
In conclusion, SLNB results in significantly less frequent lymphedema than ALND. At a median of 5 years after SLNB, approximately 5% of women will develop lymphedema. It is possible that this proportion will continue to increase with time, although data regarding the incidence of lymphedema after ALND suggest that the large majority of those who will ultimately develop it have done so by 5 years. The technique of SLNB has certainly reduced the morbidity associated with axillary staging for breast cancer; however, there remains a small but significant risk of measured lymphedema.