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Abstract

Despite the well-known safety and beneficial effects of physical activity and exercise on the well-being during and after cancer treatment, breast cancer patients commonly decrease their physical activity after the cancer diagnosis and usually remain at a low activity level throughout the treatment. Exercise interventions can prevent physical inactivity during the intervention. However, data regarding the longer-term physical activity and exercise behavior of breast cancer survivors after completing an exercise intervention is still limited. To sustainably increase the physical activity behavior well beyond the intervention phase, it is relevant to know the influencing factors. Thus, the aim of this dissertation was to investigate patterns and determinants of attendance at exercise interventions during chemotherapy and of training maintenance after the end of the interventions, considering the patients' perspective on reasons to (dis)continue exercising. The present thesis investigated these questions in the BENEFIT study, an ongoing 3-arm randomized controlled exercise intervention study in breast cancer patients undergoing neoadjuvant chemotherapy, who were either allocated to an aerobic or resistance training during the chemotherapy or a resistance training after their breast surgery. Additionally, the current evidence regarding the impact of exercise interventions on the short- and long-term physical activity behavior in breast cancer patients at different treatment stages had been investigated by conducting a systematic review and meta-analyses. The systematic review identified 27 RCTs with 4120 participants, of which 11 RCTs with 1545 participants had appropriate data for the meta-analyses. It depicted that exercise interventions may increase the physical activity behavior of breast cancer patients in the longer-run, showing small to moderate effects up to 5 years post-intervention for total physical activity and up to 20 months for moderate-to-vigorous physical activity. However, the effects decreased over time and appeared to be statistically significant for moderate-to- vigorous physical activity 6 months post-intervention only. The analyses of attendance included all 122 BENEFIT patients randomized to training during neoadjuvant chemotherapy (equally balanced in both groups). The data showed a decrease 122 Summary in attendance at the training sessions over the course of chemotherapy with an average individual attendance at 44.1% of scheduled sessions, without significant difference between aerobic and resistance training. Lower exercise attendance was associated with a higher BMI, lower education, being unpartnered, having nausea, having pain and higher level of walking in the 12 months prior to study entry. Training maintenance was analyzed with questionnaires set-up for this dissertation and completed by 68 patients (aerobic exercise: 25, resistance exercise: 29, control group: 14). They assessed the patients’ personal reasons to (dis)continue the training after completing the exercise intervention and provided an insight into the sustainability of exercise interventions. In line with the meta-analyses, the patients mostly discontinued the exercise training immediately or within 6 months after completing the exercise intervention, whereas some maintain the training for up to 60 months post-intervention. Among those who maintained the training the median continuation time was 19.0 months (Q1: 5.5 months, Q3: 36.0 months). The main reasons for training continuation were physical and psychological well-being, whereas the most frequently reported reason for training discontinuation was the change to a different exercise, followed by a lack of time and the long travel distance to the gym. The majority of patients remained active, either through maintaining their training of the exercise intervention or for those, who did not maintain their training, by changing to different exercises (52.8%). For those, who did not continue exercising nor changed to different exercise (25%), social, practical, and financial support may have enabled to establish a feasible and affordable training in their daily life after completing the exercise intervention. The BENEFIT exercise interventions successfully contributed to the uptake and maintenance of exercise in previously rather inactive breast cancer patients. Furthermore, the analyses revealed an important insight into the patient’s reasons to (dis)continue the training beyond the exercise intervention phase that enables adjustments in future studies to improve the sustainability of exercise interventions and, therewith, the physical and psychological well- being in breast cancer patients during and after cancer treatment.