Effect of radiotherapy on survival of women with locally excised ductal carcinoma in situ of the breast: a Surveillance, Epidemiology, and End Results population-based analysis.

Background: Although it has been previously reported that radiotherapy (RT) effectively reduced the incidence of local recurrence of ductal carcinoma in situ (DCIS) following breast-conserving surgery (BCS), little is known about the effect of RT on survival of patients with locally excised DCIS.

Methods: Using Surveillance, Epidemiology, and End Results registry data, we selected 56,968 female DCIS patients treated with BCS between 1998 and 2007. Overall survival (OS) and breast cancer-specific survival (BCSS) were compared among patients who received RT or no RT using the Kaplan-Meier methods and Cox proportional hazards regression models.

Results: Median follow-up was 91 months. In the multivariable model, patients receiving postoperative RT had better OS than those undergoing BCS alone (hazard ratio [HR] 0.59, 95% confidence interval [CI] 0.53-0.67, P<0.001). This pattern remained after stratification by estrogen receptor (ER) status and age. In contrast, RT delivery was not significantly associated with improved BCSS (HR 0.71, 95% CI 0.48-1.03, P=0.073). However, after stratifying by the above two variables, RT contributed to better BCSS in ER-negative/borderline patients (HR 0.41, 95% CI 0.19-0.88, P=0.023) and younger patients (≤50 years old; HR 0.37, 95% CI 0.15-0.91, P=0.030).

Conclusions: Our analysis confirms the beneficial effect of RT on OS in women with locally excised DCIS and reveals the specific protective effect of RT on BCSS in ER-negative/borderline and younger patients.