Effects of Exercise Dose and Type During Breast Cancer Chemotherapy on Longer-term Body Composition Outcomes

PURPOSE: To examine the effects of different doses and types of exercise during breast cancer chemotherapy on body composition outcomes and the associations between self-reported physical activity and body composition outcomes at 1-year follow-up. METHODS: The Combined Aerobic and Resistance Exercise (CARE) Trial randomized a total of 301 breast cancer patients during chemotherapy either to standard-dose (20-30 min/session) aerobic exercise (STAN; n=96), higher-dose (50-60 min/session) aerobic exercise (HIGH; n=101), or aerobic and resistance-combined (50-60 min/session) exercise (COMB; n=104). Each exercise program consisted of three sessions/week in supervised settings for one year. Body composition including lean body mass, whole body fat, and percent body fat was measured using dual x-ray absorptiometry. Physical activity levels were assessed by self-reported questionnaire and categorized into meeting physical activity guidelines (aerobic only; strength only; combined; and neither). Assessment was conducted at baseline, post-intervention, and 12-month follow-up. RESULTS: Of 301 patients, 284 (94.4%) and 263 (87.4%) completed body composition and self-reported physical activity assessment at 12-month follow-up, respectively. There were no significant effects of the randomized interventions on body weight, lean body mass, body fat mass, and percent body fat at 12-month follow-up; and no significant changes within each group. Meeting the combined physical activity guideline at 1-year follow-up was significantly associated with higher lean body mass compared to meeting neither guideline (+0.9 kg; p = 0.017). Moreover, meeting the aerobic guideline only was significantly associated with a lower body fat percent compared to meeting the combined guideline (-1.3%; p = 0.049) and with a higher lean body mass compared to meeting neither guideline (+0.8 kg; p = 0.037). CONCLUSIONS: Combined or higher dose aerobic exercise during breast cancer chemotherapy was not superior to a standard dose of aerobic exercise for body composition outcomes at 1-year follow-up. Meeting the combined or aerobic guidelines during follow-up, however, was associated with higher lean body mass and lower percent body fat, respectively which can have implications for breast cancer outcomes.