Pre-Diagnosis Exercise and Cardiovascular Events in Primary Breast Cancer: Women's Health Initiative

Objectives: The purpose of this study was to investigate whether pre-diagnosis exercise reduces the risk of subsequent cardiovascular events (CVEs) in women with primary breast cancer.

Background: Cardiovascular disease (CVD) is the leading nonmalignant cause of death in patients with cancer, and it is the leading cause of death in women with primary breast cancer who are older than 65 years of age.

Methods: Using a prospective design, 4,015 patients with confirmed diagnosis of primary breast cancer enrolled in the Women's Health Initiative (WHI) completed a self-report questionnaire assessing leisure-time physical activity (i.e., exercise) in metabolic equivalent task (MET) hours per week. Age- and multivariable-adjusted Cox proportional hazards models were used to estimate associations between pre-diagnosis exercise and new-onset CVEs (i.e., heart failure [HF], myocardial infarction [MI], angina, coronary revascularization, peripheral arterial disease [PAD], carotid artery disease, transient ischemic attack [TIA], stroke, and cardiovascular death).

Results: Median follow-up was 12.7 years and 8.2 years for cardiovascular disease (CVD) mortality and CVEs, respectively, with 324 CVEs, including 89 MIs, 49 new diagnoses of HF, and 215 CVD deaths. In multivariable analysis, the incidence of composite CVEs decreased across increasing total MET h/week categories (p = 0.016). Compared with <2.5 MET-hours per week, the adjusted hazard ratio (HR) was 0.80 (95% confidence interval [CI]: 0.59 to 1.09) for 2.5 to <8.6 MET h/week; 0.9 (95% CI: 0.64 to 1.17) for 8.6 to <18 MET h/week; and 0.63 (95% CI: 0.45 to 0.88) for ≥18 MET h/week.

Conclusion: Pre-diagnosis exercise exposure is associated with a significant graded reduction in subsequent CVEs in long-term survivors of primary breast cancer.