Ng WL, Wong FY
Radiation induced cardiotoxicity in breast cancer patients

Abstract Disclosures

Abstract
Background: Breast cancer radiotherapy (RT) has clear benefits for local recurrence rate and long-term survival. However, the relationship between the radiation dose exposure of cardiac substructures and the risk of radiation-induced cardiotoxicity is yet to be established. In the context of Asian breast cancer patients, this had not been well studied. Besides ischemic heart disease, RT related cardiomyopathy and heart failure are possible sequelae after RT. The risk and dose relationship have not been well described in current literature. This research will enable us to describe and quantify the impact of radiation in cardiac morbidity and mortality (all related cardiac diseases e.g ischemic heart disease, valvular disease, conduction defects, pericardial diseases) in Singapore. Dose relationship of cardiac substructures can be established and new dose constraints developed. 

Objectives: We intend to investigate the impact of radiation on cardiac morbidity and mortality in terms of radiation-induced cardiac events (e.g. ischemic heart disease, valvular disease, conduction defects, pericardial disease, etc) in breast cancer patients who received radiotherapy. We aim to establish a dose-response relationship between dose exposure of cardiac substructures and the rate of subclinical and clinical cardiac toxicities. 

Method: Retrospective review of breast cancer patients treated with RT in National Cancer Centre Singapore from 2000-2019 will be performed. The patients’ rates and time to major cardiac events, cardiac morbidity and mortality will be analysed with respect to the laterality of breast irradiation. RT doses to the heart and cardiac substructures will be extracted from RT plans to better understand the potential mechanism of cardiac injury. Analysis will be stratified by age, stage of cancer, breast RT regimen, type of surgery and the systemic treatment received. Hazard ratios for the outcomes will be estimated by Cox proportional hazards methods. Survival will be estimated by Kaplan Meier Method and compared with log-rank test.

Joint Breast Cancer Registry Singapore