313P - Ductal Carcinoma in Situ (Dcis) Treated By Mastectomy, or Local Excision with or Without Radiotherapy: a Retrospective Study About 608 Women

Abstract

ABSTRACT Aim: Since mammographic screening programmes, the proportion of DCIS has dramatically increased, and now represents 15% of newly diagnosed breast cancers in France. Adjuvant radiotherapy after local excision has become a solid option since 4 randomised trials have proven a decrease in local relapse, though failing to prove a benefit on mortality rate. DCIS is a heterogenous disease and it is unclear whether all patients uniformly benefit from currently available therapies. Methods: 608 women treated in our center for DCIS between 1983 and 2013 were retrospectively included in our study. Local excision alone was an option for DCIS less than 10mm, with low or intermediate grade, and clear margins (≥2mm). Results: The median follow-up time of 7 years. Median age was 54.5 years. Treatment consisted in mastectomy for 252 women (42%), local excision with radiotherapy (LE + RT) for 269 (44%) and local excision alone (LE) for 87 (14%). Two-hundred and eleven (35%) of patients had DCIS measuring less than 10mm, 194 (32%) between 11 and 30mm, 69 (11%) between 31 and 50mm, 55 (9%) more than 50mm and 11% (66) were multifocal. One-hundred and twelve (20%) had a low-grade DCIS, 231 (41%) an intermediate grade and 230 (39%) a high-grade. Margins were clear in a large majority of cases: 510 women (84%) had margins measuring ≥2mm, including 180 (30%) with margins ≥ 10mm; only 11 (2%) had involved margins, 64 (10%) ≤2mm and 25 (4%) were unknown. The major prognosis factors found to significantly modify local relapse rate was the type of treatment. Patients treated by LE + RT or LE showed higher relapse rate than those treated by mastectomy (HR respectively 2.06; 95%CI 1.33-3.19; p = 0.001 and 2.12; 95%CI 1.20-3.65;p = 0.007). Clear (2.1-10mm) versus involved margins decreased the relapse rate by 72% (95%CI 0.11-0.70; p = 0.007). In our selected population, women treated by LE + RT versus LE showed no significant differences in local relapses (HR 0.97; 95%CI 0.61-1.7; p = 0.91). The overall survival rate was 99.7% after ten years, with no differences between the treatment groups. Conclusions: Our monocentric retrospective study suggest that local excision alone could be an option for DCIS with good prognosis factors. Disclosure: All authors have declared no conflicts of interest.