The effect of two remote exercise programs on cardiorespiratory fitness, cardiac function, and vascular health in patients with breast cancer.

Breast cancer is a common, survivable malignancy affecting women. With improved survival, the off-target effects of chemotherapy, such as a decline in cardiorespiratory fitness and worse cardiovascular outcomes, have been recognized. Exercise training may help mitigate these effects. In this study, patients with breast cancer (N = 24) scheduled to undergo chemotherapy were randomized to either remotely administered high-intensity interval training (HIIT) or moderate-intensity exercise (MOD) based on ACSM guidelines for cancer survivors. HIIT involved three weekly sessions using the 4 × 4 protocol at 85%-90% peak heart rate (PHR), while MOD consisted of 150 min per week at 70%-75% PHR. Exercise training began 1-2 weeks before chemotherapy and continued throughout treatment. Baseline testing was conducted prior to chemotherapy and follow-up testing 7-10 days after completion. Assessments included VO2peak, echocardiography, vascular function, and blood biomarkers. VO2peak significantly declined in MOD (n = 8; 1.50 ± 0.23 to 1.27 ± 0.28 L/min; p = 0.013, d = 1.2), while remaining stable in HIIT (n = 7; 1.58 ± 0.24 to 1.52 ± 0.28 L/min; p = 0.445, d = 0.3), with a large between-group effect size (p = 0.109, d = 0.9). NTproBNP levels significantly increased in MOD (104.3 ± 35.1 to 158.1 ± 56.0; p = 0.018), but not in HIIT. The study was underpowered due to greater than anticipated dropout to detect significant between-group differences in VO2peak. These data have implications for the design of scalable exercise interventions in patients undergoing chemotherapy for breast cancer.