Session Item

Acute coronary events (ACEs) are considered the most important side effect of radiotherapy (RT) for breast cancer but underlying mechanisms still have to be identified. Process oriented models mathematically describe the development of disease, and provide a link between mechanisms and subsequent risk. Here, this link is exploited to learn about the underlying mechanisms from the observed age-time patterns of ACE risk.

A process oriented model of atherosclerosis and subsequent ACEs was applied to a contemporary breast cancer cohort of 810 patients with measurements of coronary artery calcification. Patients with prior ischemic heart disease were excluded. For each disease stage in the model, association of model parameters with mean heart dose was tested.

During a mean follow up of 9.1 years, 25 ACEs occurred. The model reproduced the prevalence and associated risk of coronary calcifications. Mean heart dose significantly improved the fit only when implemented as affecting a late stage of atherosclerosis on already existing, complicated lesions (achieving p = 0.007). This can be understood by atherosclerosis being a slowly progressing disease. Therefore, an increase of ACEs few years after RT requires advanced atherosclerosis at the time of RT.

In patients with advanced atherosclerosis, risk of ACE can increase already within a few years. Therefore, patients should be assessed for cardiovascular risk, and also elderly patients need to be considered for heart sparing techniques.