Exercise Maintenance After a Randomized Resistance Training Intervention in Breast Cancer Survivors Undergoing Adjuvant Therapy

Abstract

Exercise is highly recommended for breast cancer patients and survivors and may be increased by supervised interventions. Yet, still little is known about factors influencing the longterm physical activity behavior after the end of an Intervention. PURPOSE: To investigate the course and determinants of physical activity of breast cancer patients during and up to 12 months after a supervised resistance exercise intervention concomitant to adjuvant cancer treatment. METHODS: Physical activity was assessed in 227 breast cancer survivors before, during, and 3, 6 and 12 months after they participated in two randomized controlled trials investigating 12-week supervised resistance exercise vs. a relaxation control group concomitant to adjuvant chemotherapy (BEATE-Study, NCT01106820) or radiotherapy (BEST-Study, NCT01468766). To identify determinants of physical activity multiple ordinal logistic regression analyses were performed. RESULTS: During adjuvant therapy the intervention group exercised a median 1.8 h per week (interquartile range: 1.4-2.5), while 68% of controls did not engage in any exercise. Yet, irrespective of the intervention 32% of patients did not engage in any exercise at 12-month follow-up. Of the patients who cycled for transportation pre-diagnosis about half stopped cycling in the long run in both groups. In contrast, walking was maintained over time. Low levels of exercise at 12 months were determined by low pre-diagnosis levels of exercise (p<.001), lower education (p=0.0032), being postmenopausal (p=0.028), and having breast problems (p=0.0099) or depressive symptoms (p=0.059). At 12-month follow-up strength exercise was more common in the exercise group compared to the control Group. CONCLUSIONS: Breast cancer patients markedly decreased the exercise level and cycling for transportation after diagnosis and treatment. Yet, our resistance training intervention effectively countervailed this decline and boosted strength exercise in the months following the intervention. However, in the longer term many survivors were insufficiently active. Our results that identified subgroups especially vulnerable to physical inactivity may help to develop better individually tailored strategies to improve the physical activity behavior in breast cancer survivors in the long run.