Trends in cardiac mortality in women with ductal carcinoma in situ.

PURPOSE: In certain ductal carcinoma in situ (DCIS) subpopulations, there is no consensus regarding whether to postoperatively irradiate; decisions are often made based on potential risk of cardiac toxicities. Given the utility of Surveillance, Epidemiology, and End Results (SEER) data for studying cardiac mortality in invasive disease, this is the first such study specific for DCIS patients, evaluating trends in cardiac mortality after left-sided radiotherapy (RT). METHODS: The SEER database was queried for patients with DCIS that received RT and had known unilaterality. The central design of this study was to compare cardiac-specific mortality (CSM) between left- and right-sided DCIS patients as stratifying for "older" RT (1973-1982) versus more "modern" RT (1983-1992 or 1993-2002). Survival analysis was performed using Kaplan-Meier methodology and multivariate Cox regression modeling for factors associated with overall survival (OS) and CSS. RESULTS: Left- and right-sided patients were demographically balanced. CSM was worse for left-sided patients with DCIS diagnosed in 1973-1982 [hazard ratio (HR) 1.295; 95% confidence interval (CI) 1.182-1.420], but not in 1983-1992 (HR 1.022; 95% CI 0.949-1.100) or in 1993-2002 (HR 0.989; 95% CI 0.935-1.046)]. On multivariate analysis, laterality was not associated with OS in either decade. However, left-sided laterality was independently associated with CSM during the 1973-1982 time period, but not the more recent time periods. Examining temporal patterns in the 1973-1982 cohort, cardiac mortality was significantly increased during 10-19 and ≥20 years after diagnosis, but there was no significant increase in cardiac mortality for patients diagnosed up to 10 years after diagnosis. CONCLUSIONS: In the largest such DCIS series to date, left-sided RT was an independent risk factor for increased cardiac mortality from 1973 to 1982, but not after 1983. Using modern RT techniques and maintaining low heart doses, RT may not induce excess CSM in the DCIS population.