Impact of radiotherapy on cardiovascular health of women with breast cancer

20 December 2018

Ross Lawrenson, Chunhuan Lao, Ahmed Ali and Ian Campbell

Introduction
This study aims to examine the impact of radiotherapy on the cardiovascular health of women diagnosed with breast cancer in the Waikato region in New Zealand.

Methods
Women diagnosed with stage 0–III breast cancer and recorded in the Waikato Breast Cancer Registry were divided into two groups: a radiotherapy group and a no-radiotherapy group. Baseline characteristics and treatments were compared in the two groups. Kaplan–Meier survival analysis was performed to compare cardiovascular morbidity and mortality. Cox Proportional Hazard regression analysis was used to estimate the hazard ratio of radiotherapy on the risk of cardiovascular morbidity and mortality while adjusting for other factors.

Results
A total of 3528 women were included in this study, with 2303 in the radiotherapy group and 1225 in the no-radiotherapy group. At 10-year followup, 11.7% of women in the radiotherapy group and 19.4% in the no-radiotherapy group experienced cardiovascular events. Only 2.3% of patients who received radiotherapy died of cardiovascular disease by 10  years compared to 7.0% in the no-radiotherapy group. After adjusting for clinically significant factors, there was unexplained reduced risk of developing cardiovascular disease in the radiotherapy group compared to the no-radiotherapy group (HR 0.73, 95% CI: 0.59–0.92). No significant difference was found in cardiovascular mortality between the two groups.

Conclusions
Radiotherapy appears less likely to be offered to patients at higher risk of cardiovascular disease. No evidence of increased risk of a cardiovascular event was found in the group of women with breast cancer treated with radiotherapy and current regimens appear safe. Traditional cardiovascular risk factors remain the main culprits in this setting. Clinicians should work with patients in managing these risk factors for optimal results.