Determinants of Cardiovascular Health in Breast Cancer Survivors Based on Physical Activity Status

Abstract

While the worldwide incidence of breast cancer is high, the New Zealand 5-year survival rate is encouraging at 86% which can be attributed to improvements in screening programmes and technological advances in chemotherapy (CT) and radiation therapies (RT). However, many anticancer therapies have potentially debilitating side-effects, including the development of cardiac toxicity, reductions in cardiorespiratory fitness and changes in body composition. Although it is well known that these treatments are associated with a relatively high risk of developing both cardiac and endothelial dysfunction, possible determinants of cardiovascular health (CV) in cancer survivors remains unknown. However, across numeral clinical populations such as coronary artery disease and hypertensive individuals, physical activity (PA) has been shown to have a cardio-protective effect on the CV system. Therefore, the purpose of this study was to provide insight into CV health of breast cancer survivors previously treated with CT and/or RT, based on PA status. Specific aims were to investigate whether PA status determines central blood pressures (cBP) and arterial stiffness within this population. A second aim was to investigate whether cardiorespiratory fitness and/or body composition may moderate CV health following these treatments. This study used a cross-sectional design with participants being women previously treated with RT and/or CT for breast cancer who were classified as either physically active (n=44) or inactive (n=21) based on current PA status. The International Physical Activity Questionnaire (IPAQ) Long Form was used to evaluate PA level. A vascular health assessment assessed arterial stiffness and central blood pressures, while a submaximal treadmill walking test was used to estimate VO2max. Body composition was measured by dual energy X-ray absorptiometry. A multiple linear regression was utilised for statistical testing. Active participants had significantly lower central blood pressures (SBP: 111±12 mmHg vs. 120±13 mmHg, p=0.012; DBP: 72±6 mmHg vs. 79±7 mmHg, p=0.000) compared to inactive participants; however, arterial stiffness was similar between the two study groups (p=0.659). Linear regression models showed that V ̇O2max is a predictor of arterial stiffness (AIx %) and approached significance with myocardial efficiency (indicated by the use of double product, DP); however, the association between V ̇O2max and AIx becomes non-significant after adjusting for age. Fat mass (%) (FM %) was found to be an important moderator of DP not AIx, even after adjusting for both age and V ̇O2max.. The novel results from the current study suggest that there is an association between higher levels of recreational PA and lower cBP’s in breast cancer survivors following treatment. Secondly, FM (%) was identified as an important moderator of myocardial efficiency, with V ̇O2max a predictor of arterial stiffness. Identifying possible determinants of CV health is imperative for reducing the incidence of cardiovascular disease development and mortality in breast cancer patients following treatment.