Breast Cancer Radiation Therapy and the Risk of Acute Coronary Events: Insights From a Process-Oriented Model.

PURPOSE: Acute coronary events (ACEs) are considered the most important side effect of radiation therapy (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. METHODS AND MATERIALS: 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. The process-oriented model describes disease development as a series of different stages. Different variants of the model were fitted to the data. In each variant, one stage was assumed to be accelerated in relation to mean heart dose. RESULTS: 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 = .007). This can be understood by atherosclerosis being a slowly progressing disease. Therefore, an increase in ACEs a few years after RT requires advanced atherosclerosis at the time of RT. CONCLUSIONS: Risk of ACE increases within a few years in patients with advanced atherosclerosis at RT. Therefore, patients should be assessed for cardiovascular risk, and older patients need to be considered for heart-sparing techniques.

Ischemic heart disease in workers at Mayak PA: latency of incidence risk after radiation exposure.

We present an updated analysis of incidence and mortality from atherosclerotic induced ischemic heart diseases in the cohort of workers at the Mayak Production Association (PA). This cohort constitutes one of the most important sources for the assessment of radiation risk. It is exceptional because it comprises information on several other risk factors. While most of the workers have been exposed to external gamma radiation, a large proportion has additionally been exposed to internal radiation from inhaled plutonium. Compared to a previous study by Azizova et al. 2012, the updated dosimetry system MWDS-2008 has been applied and methods of analysis have been revised. We extend the analysis of the significant incidence risk and observe that main detrimental effects of external radiation exposure occur after more than about 30 years. For mortality, significant risk was found in males with an excess relative risk per dose of 0.09 (95% CI: 0.02; 0.16) [Formula: see text] while risk was insignificant for females. With respect to internal radiation exposure no association to risk could be established.