Exercise during cancer treatment improves cancer‐related fatigue (CRF), but the importance of exercise intensity for CRF is unclear. We compared the effects of high‐ vs low‐to‐moderate‐intensity exercise with or without additional behavior change support (BCS) on CRF in patients undergoing (neo‐)adjuvant cancer treatment. This was a multicenter, 2x2 factorial design randomized controlled trial (Clinical Trials NCT02473003) in Sweden. Participants recently diagnosed with breast (n = 457), prostate (n = 97) or colorectal (n = 23) cancer undergoing (neo‐)adjuvant treatment were randomized to high intensity (n = 144), low‐to‐moderate intensity (n = 144), high intensity with BCS (n = 144) or low‐to‐moderate intensity with BCS (n = 145). The 6‐month exercise intervention included supervised resistance training and home‐based endurance training. CRF was assessed by Multidimensional Fatigue Inventory (MFI, five subscales score range 4‐20), and Functional Assessment of Chronic Illness Therapy‐Fatigue scale (FACIT‐F, score range 0‐52). Multiple linear regression for main factorial effects was performed according to intention‐to‐treat, with post‐intervention CRF as primary endpoint. Overall, 577 participants (mean age 58.7 years) were randomized. Participants randomized to high‐ vs low‐to‐moderate‐intensity exercise had lower physical fatigue (MFI Physical Fatigue subscale; mean difference −1.05 [95% CI: −1.85, −0.25]), but the difference was not clinically important (ie <2). We found no differences in other CRF dimensions and no effect of additional BCS. There were few minor adverse events. For CRF, patients undergoing (neo‐)adjuvant treatment for breast, prostate or colorectal cancer can safely exercise at high‐ or low‐to‐moderate intensity, according to their own preferences. Additional BCS does not provide extra benefit for CRF in supervised, well‐controlled exercise interventions.

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Exercise training has been hypothesized to lower the inflammatory burden for patients with cancer, but the role of exercise intensity is unknown. To this end, we compared the effects of high-intensity (HI) and low-to-moderate intensity (LMI) exercise on markers of inflammation in patients with curable breast, prostate and colorectal cancer undergoing primary adjuvant cancer treatment in a secondary analysis of the Phys-Can randomized trial (NCT02473003). Sub-group analyses focused on patients with breast cancer undergoing chemotherapy. Patients performed six months of combined aerobic and resistance exercise on either HI or LMI during and after primary adjuvant cancer treatment. Plasma taken at baseline, immediately post-treatment and post-intervention was analyzed for levels of interleukin (IL)-1β, IL-6, IL-8, IL-10, tumor necrosis factor (TNF)-α and C-reactive protein (CRP). Intention-to-treat analyses of 394 participants revealed no significant between-group differences. Regardless of exercise intensity, significant increases of IL-6, IL-8, IL-10 and TNF-α post-treatment followed by significant declines, except for IL-8, until post-intervention were observed with no difference for CRP or IL-1β. Subgroup analyses of 154 patients with breast cancer undergoing chemotherapy revealed that CRP (Estimated Mean Difference (95% CI): 0.59 (0.33; 1.06); p = 0.101) and TNF-α (EMD (95% CI): 0.88 (0.77; 1) ; p = 0.053) increased less with HI exercise post-treatment compared to LMI. Exploratory cytokine co-regulation analysis revealed no difference between the groups. In patients with breast cancer undergoing chemotherapy, HI exercise resulted in a lesser increase of CRP and TNF-α immediately post-treatment compared to LMI, potentially protecting against chemotherapy related inflammation.

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Introduction: (Neo-)adjuvant chemotherapy for breast cancer has a deleterious impact on muscle tissue resulting in reduced cardiorespiratory fitness, skeletal muscle mass and function. Physical exercise during treatment may counteract some of these negative effects. However, the effects of resistance training (RT) alone have never been explored. The present study aims to investigate if heavy-load RT during (neo-)adjuvant chemotherapy counteracts deleterious effects on skeletal muscle in women diagnosed with breast cancer. We hypothesize that (neo-)adjuvant treatment with chemotherapy will reduce muscle fiber size, impair mitochondrial function, and increase indicators of cellular stress and that RT during treatment will counteract these negative effects. We also hypothesize that RT during (neo-)adjuvant chemotherapy will increase muscle and blood levels of potential antitumor myokines and reduce treatment-related side effects on muscle strength and cardiorespiratory fitness. Methods: Fifty women recently diagnosed with breast cancer scheduled to start (neo-)adjuvant chemotherapy will be randomized to either randomized to either intervention group or to control group. The intervention group will perform supervised heavy-load RT twice a week over the course of chemotherapy (approximately 16-weeks) whereas the control group will be encouraged to continue with their usual activities. Muscle biopsies from m. vastus lateralis will be collected before the first cycle of chemotherapy (T0), after chemotherapy (T1), and 6 months later (T2) for assessment of muscle cellular outcomes. The primary outcome for this study is muscle fiber size. Secondary outcomes are: regulators of muscle fiber size and function, indicators of cellular stress and mitochondrial function, myokines with potential antitumor effects, muscle strength, and cardiorespiratory fitness. Ethics and dissemination: Ethical approval has been obtained from the Regional Ethical Review Board in Uppsala, Sweden (Dnr:2016/230/2). Results will be disseminated through presentations at scientific meetings, publications in peer-reviewed journals, social media, and patient organizations. Trial registration number: NCT04586517.