Background: Many of the 2.4 million breast cancer survivors in the United States are at risk of breast cancer– associated lymphedema as a result of axillary surgery. One-third of patients require axillary node dissection, which is associated with a 13 to 47 percent risk of lymphedema; even lymphatic-sparing surgery, such as sentinel node biopsy, causes lymphedema in 5 to 7 percent of patients. Arm lymphedema causes swelling and discomfort, impairs arm function, and decreases quality of life. Women at risk often restrict activities with the affected arm and are sometimes instructed not to lift children or other heavy objects. Paradoxically, such protective actions may discourage healthy exercise, leading to deconditioning and increased risk of injury and possibly lymphedema onset. To test the safety of weight-bearing exercise in breast cancer survivors, Schmitz and colleagues conducted the Physical Activity and Lymphedema trial.

The Study: This randomized controlled trial followed a smaller pilot study that did not find any evidence that regular weight lifting precipitated lymphedema. The authors randomized women to two groups: one year of supervised progressive weight lifting versus no intervention. The primary outcomes were the effect of weight lifting on established lymphedema (published previously) and the incidence of lymphedema in the weight-lifting group. Women were included if they had a one- to five-year history of unilateral, nonmetastatic breast cancer with no history or current evidence of lymphedema; a body mass index of 50 kg per m² or less; no other medical conditions that would preclude weight-lifting exercise; and no intentional weight loss or participation in a weight-lifting program in the previous year. Participants were placed in two groups of equal size through a computerized program to balance potential confounders at baseline, including age (younger than 54 years versus 54 years and older), number of lymph nodes removed (less than six versus six or more), obesity (body mass index less than 30 versus 30 or more), and history of radiation treatment (yes versus no). Women in the intervention group received a one-year membership to a fitness center near their home. They participated in twice-weekly supervised upper- and lower-body weight lifting for 13 weeks, and then continued with unsupervised progressive weight training twice weekly for the remainder of the year. Those in the control group were asked not to change their baseline activity levels and were offered a one-year gym membership after the study period.

Lymphedema was defined as at least a 5 percent increase in arm swelling and at least a 5 percent interlimb water volume difference. Arm swelling was assessed by water volume displacement at baseline and at 12 months. Fitness trainers or study measurement staff also measured arm volumes monthly. In addition, participants were formally evaluated for lymphedema if they experienced symptoms lasting at least one week.

Results: The study was adequately powered to detect more than a doubling of the background 6 percent rate of incident lymphedema. At 12 months, there was no significant difference between groups in the number of women developing a 5 percent or greater increase in arm volume (17 percent [13 of 75 women] in the control group versus 11 percent [eight of 72 women] in the weight-lifting group). No differences in the number and severity of symptoms were noted. A subgroup analysis of women with five or more lymph nodes removed was also performed. Among these women, the proportion who experienced a 5 percent or more increase in arm volume was significantly lower in the weight-lifting group (7 percent [three of 45] in the weight-lifting group versus 22 percent [11 of 49] in the control group).

Conclusion: Slowly progressive weight lifting does not contribute to lymphedema in breast cancer survivors, and may be beneficial in women who have had five or more lymph nodes removed.