Risk of Ischemic Heart Disease After Radiotherapy for Breast Cancer
Posted: Tuesday, March 24, 2020
Women who received adjuvant radiotherapy for left-sided breast cancer between 1992 and 2012 had an increased risk of ischemic heart disease compared with those treated for right-sided breast cancer, according to a population-based cohort study published in Breast Cancer Research. According to Malin Sund, MD, of Umea University, Sweden, and colleagues, “The results emphasize the importance of further developing and implementing radiotherapy techniques that lower the cardiac doses, without compromising the beneficial effects of radiotherapy.”
The study included 60,217 women with breast cancer and 300,791 age-matched women with no history of breast cancer from The Breast Cancer DataBase Sweden. Of the women with breast cancer, 28,903 had right-sided breast tumors, 30,840 had left-sided breast tumors, and 474 women had bilateral or unknown breast tumors. The average follow-up time was 8.1 years for those with breast cancer and 9.0 years for women without breast cancer.
Women with left-sided breast cancer had a greater risk of ischemic heart disease than women with right-sided breast cancer, with a hazard ratio of 1.09. Among women who received radiotherapy, the authors found a hazard ratio of 1.18 in those with left-sided compared with right-sided breast cancer. The hazard ratios for ischemic heart disease in women with left-sided versus right-sided breast cancer were even higher with more extensive lymph node metastasis and with added endocrine therapy or chemotherapy.
Of note, over the study time period (1992–2012), the standard radiotherapy was three-dimensional conformal radiotherapy given with tangential fields; breathing adaption techniques such as deep inspiratory breath-hold had not yet been adopted. Information on the patients’ radiation doses and targets was not available, but the breast cancer treatment guidelines during most of the study period recommended a dose of 2 to 50 Gy over 5 weeks.
Disclosure: The study authors reported no conflicts of interest.