Abstract 12732: Risk of Heart Failure After Contemporary Radiotherapy for Breast Cancer in the Community

Abstract

Background: Contemporary breast cancer radiotherapy (RT) results in variable cardiac radiation exposure. While cardiomyocytes are radio-resistant, radiation induces coronary microvascular endothelial damage and inflammation which may ultimately lead to myocardial inflammation, ischemia and fibrosis and put patients at risk for heart failure (HF) and particularly, HF with preserved ejection fraction (HFpEF). Methods: Community based (Olmsted County, MN), HF case-control study of contemporary (1999-2014) breast cancer RT patients with CT-based RT planning for precise mean cardiac radiation dose (MCRD) calculation. HF cases (n=66) and controls (n=129) were matched (1:2) for age at RT, HF risk factors, tumor side and chemotherapy use. Matched controls and cases had identical follow-up (index interval). Proportion of HF and clinical characteristics in categories of MCRD were reported (table) and conditional logistic regression was used to estimate the HF odds ratio (OR) associated with MCRD as a continuous variable. Results: Of the 66 HF cases, 46 (70%) had HFpEF and 20 (30%) had HF with reduced ejection fraction (HFrEF). The proportion of patients with HF (any) or HFpEF increased and proportion with HFrEF tended to increase with increasing MCRD. The prevalence of HF risk factors (hypertension, diabetes, coronary disease) at time of RT did not vary by MCRD while left sided tumor, cancer stage and adriamycin use increased with increasing MCRD. The OR per 1 unit increase in log MCRD was 3.71 (1.98, 6.94) for total HF (p<0.001), 4.91 (1.93, 9.09) for HFpEF (p<0.001) and 2.78 (0.91, 8.47) for HFrEF (p=0.07). The mean index interval was 5.0±3.2 years. Conclusion: Cardiac radiation incident to contemporary breast RT increases the risk of HF, and particularly HFpEF over a short post-RT interval. These data may guide use of proton beam therapy in breast cancer. These data also provide support for the role of coronary microvascular compromise in the pathophysiology of HFpEF.