Mortality from cardiovascular disease in women with breast cancer - a nationwide registry study

Background: Only few existing studies have investigated the mortality from cardiovascular disease (CVD) in women with breast cancer (BC). The aim of this study was to investigate CVD mortality in patients with BC compared with a matched control group without BC using national registry data. Material and methods: We followed 16,505 Danish women diagnosed with BC in 2003–2007 up to 10 years after BC diagnosis compared with 165,042 matched controls from the general Danish population. The matching criteria included gender, age, region of residence, and education. We performed multivariate Cox regression analyses to investigate the influence of preexisting CVD on mortality. Moreover, we used the cumulative incidence and conditional probability functions to study the risk of CVD-related death in the presence of competing risk, i.e., the risk of dying from other causes than CVD. Results: We found that preexisting CVD increased both overall mortality and CVD mortality in both patients with BC and controls. Furthermore, we found that patients with BC were at lower risk of dying from CVD up to 10 years after BC diagnosis compared with controls. The cumulative incidence of CVD as underlying cause of death was 4.0% in patients with BC and 5.7% in controls after 10 years. The most common CVD-related causes of death were ischemic heart disease including acute coronary syndrome, cerebrovascular accident, heart failure, and atrial fibrillation. Discussion: Our study contributes to the growing body of work on BC and comorbidities and highlights the importance of CVD in individuals with BC. Further studies are needed to confirm our finding that patients with BC are at lower risk of dying from CVD up to 10 years after BC diagnosis compared with a matched control group without BC.