Risk of ischemic heart disease after radiotherapy for ductal carcinoma in situ

Abstract

PurposeThe use of adjuvant radiotherapy (RT) in the management of ductal carcinoma in situ (DCIS) is increasing. Left-sided breast irradiation may involve exposure of the heart to ionising radiation, increasing the risk of ischemic heart disease (IHD). We examined the incidence of IHD in a population-based cohort of women with DCIS.MethodsThe Breast Cancer DataBase Sweden (BCBase) cohort includes women registered with invasive and in situ breast cancers 1992–2012 and age-matched women without a history of breast cancer. In this analysis, 6270 women with DCIS and a comparison cohort of 31,257 women were included. Through linkage with population-based registers, data on comorbidity, socioeconomic status and incidence of IHD was obtained. Hazard ratios (HR) for IHD with 95% confidence intervals (CI) were analysed.ResultsMedian follow-up time was 8.8 years. The risk of IHD was not increased for women with DCIS versus women in the comparison cohort (HR 0.93; 95% CI 0.82–1.06), after treatment with radiotherapy versus surgery alone (HR 0.77; 95% CI 0.60–0.98) or when analysing RT by laterality (HR 0.85; 95% CI 0.53–1.37 for left-sided versus right-sided RT).ConclusionsThe risk of IHD was lower for women with DCIS allocated to RT compared to non-irradiated women and to the comparison cohort, probably due to patient selection. Comparison of RT by laterality did not show any over-risk for irradiation of the left breast.