Cardiorespiratory fitness in breast cancer survivors

Maximal oxygen uptake (VO(2max)) has been used to assess risk for all-cause mortality and cardiovascular disease (CVD), and low VO(2max) has recently been associated with increased mortality from breast cancer. The purpose of this study was to determine the proportion of breast cancer survivors with 2 or more risk factors for CVD exhibiting a low VO(2max) and to determine whether sub-maximal endpoints which could be applied more readily to intervention research would correlate with the maximal treadmill test. We performed a single VO(2max) test on a treadmill with 30 breast cancer survivors age 30–60 (mean age 50.5 ± 5.6 years) who had 2 or more cardiac risk factors for CVD not related to treatment and who had received systemic therapy and or left chest radiation. Submaximal VO(2) endpoints were assessed during the VO(2max) treadmill test and on an Arc trainer. Resting left ventricular ejection fraction (LVEF) was also assessed by echocardiogram (ECHO) or multi-gated acquisition scan (MUGA). A majority (23/30) of women had a VO(2max) below the 20th percentile based on their predicted normal values. The group mean resting LVEF was 60.5 ± 5.0%. Submaximal VO(2) measures were strongly correlated with the maximal test including; 1) 85% age predicted maximum heart rate VO(2) on treadmill, (r = .89; p < 0.001), 2) treadmill VO(2) at anaerobic threshold (AT), (r = .83; p < 0.001), and 3) Arc VO(2) at AT, (r = .80; p < 0.001). Breast cancer survivors with 2 or more CVD risk factors but normal LVEF had a low cardiorespiratory fitness level compared to normative values in the healthy population placing them at increased risk for breast cancer and cardiovascular mortality. Submaximal VO(2) exercise testing endpoints showed a strong correlation with the VO(2max) test in breast cancer survivors and is a good candidate for testing interventions to improve cardiorespiratory fitness.