In women with ductal carcinoma in situ (DCIS), breast-conserving treatment combined with radiotherapy reduces the risk for local recurrence (LR), a recent study indicates.

Adjuvant radiotherapy after a local excision for DCIS is intended to reduce the incidence of LR, wrote Mila Donker, MD, of the Netherlands Cancer Institute in Amsterdam, the Netherlands, and colleagues in Journal of Clinical Oncology. To analyze the long-term risk for LR and its impact on survival following breast-conserving surgery for DCIS, the investigators randomized patients with complete local excision of DCIS (less than 5 cm) to no further treatment (503 women) or to radiotherapy (507 women). Randomization took place between 1986 and 1996, as part of the phase 3 European Organization for Research and Treatment of Cancer (EORTC) 10853 trial.

Over a median follow-up of 15.8 years, radiotherapy reduced the risk for any LR by 48%. The 15-year LR-free rate was 82% among the radiotherapy patients, compared with 69% in the local-excision-only group. The 15-year invasive LR-free rate was 90% among the radiotherapy users and 84% for the other women.

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The differences in LR between groups did not lead to differences in breast cancer–specific survival or in overall survival. However, both those measures were significantly worse for women with invasive LR compared with women who did not experience recurrence. Radiotherapy after breast-conserving surgery for DCIS resulted in a lower overall salvage mastectomy rate, at 13% vs 19% for the excision-only group.

“At 15 years, almost one in three nonirradiated women developed an LR after [local excision] for DCIS,” noted Donker and coauthors. “[Radiotherapy] reduced this risk by a factor of 2. Although women who developed invasive recurrence had worse survival, the long-term prognosis was good and independent of the given treatment.”