Breast-conserving treatment for ductal carcinoma in situ: Impact of boost and tamoxifen on local recurrences.

PURPOSE: Ductal carcinoma in situ represents 15 to 20% of all breast cancers. Breast-conserving surgery and whole breast irradiation was performed in about 60% of the cases. This study reports local recurrence rates in patients with ductal carcinoma in situ treated by breast-conserving surgery and whole breast irradiation with or without boost and/or tamoxifen and compares different therapeutic options in two European countries. PATIENTS AND METHODS: From 1998 to 2007, 819 patients with pure ductal carcinoma in situ were collected, both in France (266) and Italy (553). Median age was 56. All underwent breast-conserving surgery and whole breast irradiation; 391 (48%) received a boost (55% in France and 45% in Italy, P=0.017) and 173 (22.5%) tamoxifen (4.5% in France and 32% in Italy, P<0.0001). RESULTS: With a 90-month median follow-up, there were 51 local recurrences (6.2%), including 27 invasive (53%). The 5- and 10-year local recurrence rates were 4% and 8.6%. Two patients developed axillary recurrence and 12 (1.5%) metastases (seven after invasive local recurrence); 41 (5%) patients had contralateral breast cancer. In the multivariate analysis, high nuclear grade and lack of tamoxifen are the most powerful predictors of local recurrence, with 2.6 (95% confidence interval [95% CI]: 1.74-3.89, P=0.0012) and 2.85 (95% CI: 1.42-5.72, P=0.04) odds ratio (OR) estimates, respectively. Age, margin status and boost did not influence local recurrence rates. CONCLUSIONS: This study confirms the ductal carcinoma in situ treatment heterogeneity among countries and the unfavourable prognostic role of nuclear grade. Tamoxifen reduces local recurrence rates and might be considered for some subgroups of patients, but further confirmation is required. The boost usefulness still remains unclear.