Effects of High and Low-To-Moderate Intensity Exercise During (Neo-) Adjuvant Chemotherapy on Muscle Cells, Cardiorespiratory Fitness, and Muscle Function in Women With Breast Cancer: Protocol for a Randomized Controlled Trial

BACKGROUND: (Neo-)adjuvant chemotherapy for breast cancer is effective but has deleterious side effects on muscle tissue, resulting in reduced skeletal muscle mass, muscle function, and cardiorespiratory fitness. Various exercise regimens during cancer treatment have been shown to counteract some of these side effects. However, no study has compared the effect of high-intensity training versus low-to-moderate intensity training on muscle tissue cellular outcomes and physical function in patients with breast cancer during chemotherapy. OBJECTIVE: The aim of this substudy within the Physical Training in Cancer (Phys-Can) consortium is to evaluate and compare the effects of high and low-to-moderate intensity exercise on muscle cellular outcomes, muscle function, and cardiorespiratory fitness in women with breast cancer undergoing (neo-)adjuvant chemotherapy. We further aim to investigate if the effects of chemotherapy including taxanes on muscles will be different from those of taxane-free chemotherapy. METHODS: Eighty women recently diagnosed with breast cancer scheduled to start (neo-)adjuvant chemotherapy will be randomized to a combination of strength and endurance training, either at high intensity or at low-to-moderate intensity. Testing of muscle function and cardiorespiratory fitness and collection of muscle biopsies from the vastus lateralis muscle will be performed before the first cycle of chemotherapy (or after 1 week, when not possible) (T0), halfway through chemotherapy (T1), and after completion of chemotherapy (T2). It is estimated that approximately 50% of the participants will be willing to undergo muscle biopsies. To separate the effect of the treatment itself, a usual care group with no supervised training will also be included, and in this group, testing and collection of muscle biopsies will be performed at T0 and T2 only. RESULTS: This study is funded by Active Against Cancer (Aktiv mot kreft) (May 2013) and the Norwegian Cancer Society (December 2018). Inclusion started in December 2016 and the last participant is expected to be recruited in December 2022. As of June 2022, we enrolled 38 (19 with biopsies) participants to the high-intensity training group, 36 (19 with biopsies) participants to the low-to-moderate intensity training group, and 17 (16 with biopsies) participants to the usual care group. Data analyses will start in fall 2022. The first results are expected to be published in spring 2024. CONCLUSIONS: This study will generate new knowledge about the effects of different training intensities for women with breast cancer during chemotherapy treatment. It will give further insight into how chemotherapy affects the muscle tissue and how physical training at different intensities may counteract the treatment side effects in muscles. The results of this study will inform the development and refinement of exercise programs that are effective and compatible with the multidisciplinary management of breast cancer. TRIAL REGISTRATION: ClinicalTrials.gov NCT05218876; https://tinyurl.com/ysaj9dhm INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID): DERR1-10.2196/40811