Association of self-directed walking with toxicity moderation during chemotherapy for the treatment of early breast cancer.

ABSTRACT

BACKGROUND: In the field of exercise oncology, there is a need to quantify the potential benefits of moderate, self-directed physical activity during active treatment. In a pooled analysis of three identical single-arm intervention studies, we investigate the association of activity tracker steps with patient-reported toxicities during chemotherapy. METHODS: Women with early breast cancer who were enrolled in the intervention studies reported their symptom severity every 2-3 weeks throughout chemotherapy, and daily steps were documented through a Fitbit activity tracker. Relative risks (RR) and 95% confidence intervals (CI) were calculated using Poisson regression models with robust variance. For outcomes significant in unadjusted models, adjusted RRs were calculated controlling for race, age, and education level. Tracker step cut point (high step, low step) was determined by the means. Cumulative incidence functions of moderate, severe, and very severe (MSVS) symptoms were estimated using the Kaplan-Meier method and compared using a Cox proportional hazard model. RESULTS: In a sample of 283 women, mean age was 56 years and 76% were White. Mean tracker-documented steps/week were 29,625, with 55% walking below the mean (low step) and 45% above (high step). In multivariable analysis, high step patients had lower risk for fatigue [RR 0.83 (0.70, 0.99)] (p = 0.04), anxiety [RR 0.59 (0.42, 0.84)] (p = 0.003), nausea [RR 0.66 (0.46, 0.96)] (p = 0.03), depression [RR 0.59 (0.37, 0.03)] (p = 0.02), and ≥ 6 MSVS symptoms [RR 0.73 (0.54, 1.00)] (p = 0.05) and had 36% lower risk for dose reductions [RR 0.64 (95% CI 0.43, 0.97)] (p = 0.03). CONCLUSION: Self-directed walking at a rate of at least 30,000 steps/week may moderate the severity of treatment side effects during chemotherapy for early breast cancer. TRIAL NUMBERS NCT02167932, NCT02328313, NCT03761706.