Following breast-conserving surgery for DCIS, reexcision before radiotherapy is recommended when margins are close or involved. We investigated whether an additional radiation dose could replace reexcision. We selected 208 women with DCIS of the breast treated with breast-conserving surgery between 1992 and 2002 who had either close margins (< 2 mm) (89 pts) or focally (< 1 mm) or minimally (1–15 mm) involved margins (119 pts). Sixty-one patients (29%) underwent reexcision before irradiation and 147 patients (71%) received breast irradiation with boost, without reexcision.

Results Median follow-up was 89 months. Median age was 53 years with 7 patients less than 41. Involved margins were less frequent in the non reexcision group than in the reexcised group (50% vs. 74%, p = 0.0019). All other clinical and histological features were comparable. Median whole-breast radiation dose was 50 Gy. Median total doses to the tumour bed were 67 Gy (range, 45–77) and 60 Gy (range, 46–74), respectively (p < 0.0001). Of the 61 reexcised patients, 56% had residual DCIS and 6% had invasive cancer. Six underwent a mastectomy for persistent margin involvement. Seven-year locoregional failure rates were 9.3% without, and 9.6% with reexcision (ns). No differences were observed when adjusting for margin status.

Conclusion
In carefully selected patients with close (< 2 mm) or focally/minimally involved margins, reexcision may be avoided and satisfactory local control achieved by increasing the radiation dose to the tumour bed to at least 66 Gy. These results only apply to patients older than 40 and would need confirmation in independent series.