Determinants of exercise intolerance in breast cancer patients prior to anthracycline chemotherapy

Women with early‐stage breast cancer have reduced peak exercise oxygen uptake (peak VO(2)). The purpose of this study was to evaluate peak VO(2) and right (RV) and left (LV) ventricular function prior to adjuvant chemotherapy. Twenty‐nine early‐stage breast cancer patients (mean age: 48 years) and 10 age‐matched healthy women were studied. Participants performed an upright cycle exercise test with expired gas analysis to measure peak VO(2). RV and LV volumes and function were measured at rest, submaximal and peak supine cycle exercise using cardiac magnetic resonance imaging. Peak VO(2) was significantly lower in breast cancer patients versus controls (1.7 ± 0.4 vs. 2.3 ± 0.5 L/min, P = 0.0013; 25 ± 6 vs. 35 ± 6 mL/kg/min, P = 0.00009). No significant difference was found between groups for peak upright exercise heart rate (174 ± 13 vs. 169 ± 16 bpm, P = 0.39). Rest, submaximal and peak exercise RV and LV end‐diastolic and end‐systolic volume index, stroke index, and cardiac index were significantly lower in breast cancer patients versus controls (P < 0.05 for all). No significant difference was found between groups for rest and exercise RV and LV ejection fraction. Despite preserved RV and LV ejection fraction, the decreased peak VO(2) in early‐stage breast cancer patients prior to adjuvant chemotherapy is due in part to decreased peak cardiac index secondary to reductions in RV and LV end‐diastolic volumes.