Exercise and health-related fitness predictors of chemotherapy completion in breast cancer patients: pooled analysis of two multicenter trials

Abstract

Purpose: Achieving a higher chemotherapy completion rate is associated with better outcomes in breast cancer patients. We examined the role of exercise and health-related fitness variables in predicting chemotherapy completion in early stage breast cancer patients.

Methods: We pooled data from two large, multicenter, exercise trials that obtained baseline (pre-chemotherapy) measures of exercise and health-related fitness in 543 breast cancer patients initiating adjuvant chemotherapy. Assessments included body composition, cardiovascular fitness, muscular strength, patient-reported physical functioning, and self-reported exercise behavior. Chemotherapy completion was assessed as the average relative dose intensity (RDI) for the originally planned regimen. We used logistic regression analyses with a two-sided p value of < 0.05 to estimate the associations between the predictors and an RDI of ≥ 85%.

Results: Overall, 432 of 543 (79.6%) breast cancer patients received an RDI of ≥ 85%. In logistic regression analyses adjusted for significant covariates, patients in the highest 20% vs. lowest 80% of absolute VO_2peak were significantly more likely to complete ≥ 85% RDI (89.0% vs. 77.2%; OR_adj 2.06, 95% CI 1.07-3.96, p = 0.031). Moreover, patients in the highest 80% vs. lowest 20% of absolute chest strength were significantly more likely to complete ≥ 85% RDI (81.5% vs. 71.4%; OR_adj 1.80, 95% CI 1.09-2.98, p = 0.021).

Conclusions: In these exploratory analyses, higher baseline (pre-chemotherapy) cardiovascular fitness and muscular strength were associated with higher rates of chemotherapy completion in early stage breast cancer patients. Aerobic and/or strength training interventions that increase cardiovascular fitness and muscular strength prior to chemotherapy for breast cancer may improve treatment tolerability and outcomes.

Clinical trial registration: START: NCT00115713, June 24, 2005; CARE: NCT00249015, November 7, 2005 ( http://clinicaltrials.gov ).

Keywords: Body composition; Breast cancer; Chemotherapy; Exercise; Physical fitness.