Abstract

Purpose Adjuvant radiotherapy (RT) after a local excision (LE) for ductal carcinoma in situ (DCIS) aims at reduction of the incidence of a local recurrence (LR). We analyzed the long-term risk on developing LR and its impact on survival after local treatment for DCIS. Patients and Methods Between 1986 and 1996, 1,010 women with complete LE of DCIS less than 5 cm were randomly assigned to no further treatment (LE group, n = 503) or RT (LE+RT group, n = 507). The median follow-up time was 15.8 years. Results Radiotherapy reduced the risk of any LR by 48% (hazard ratio [HR], 0.52; 95% CI, 0.40 to 0.68; P < .001). The 15-year LR-free rate was 69% in the LE group, which was increased to 82% in the LE+RT group. The 15-year invasive LR-free rate was 84% in the LE group and 90% in the LE+RT group (HR, 0.61; 95% CI, 0.42 to 0.87). The differences in LR in both arms did not lead to differences in breast cancer–specific survival (BCSS; HR, 1.07; 95% CI, 0.60 to 1.91) or overall survival (OS; HR, 1.02; 95% CI, 0.71 to 1.44). Patients with invasive LR had a significantly worse BCSS (HR, 17.66; 95% CI, 8.86 to 35.18) and OS (HR, 5.17; 95% CI, 3.09 to 8.66) compared with those who did not experience recurrence. A lower overall salvage mastectomy rate after LR was observed in the LE+RT group than in the LE group (13% v 19%, respectively). Conclusion At 15 years, almost one in three nonirradiated women developed an LR after LE for DCIS. RT reduced this risk by a factor of 2. Although women who developed an invasive recurrence had worse survival, the long-term prognosis was good and independent of the given treatment.