e11008 Background: Breast cancer recurrences in the previously irradiated breast lead to mastectomy. An option to avoid mastectomy and offer BCS to patients with recurrent breast cancer is intraoperative radiotherapy. Methods: Between 04/02 and 11/09, 22 patients (median age 65.9 yrs, range, 42.8-86.9) received IORT during BCS to treat in- breast tumor recurrence (IBTR) after previous radiation after a median of 154 ± 54 months (range, 34-219). Fourteen patients had ductal-invasive carcinoma, 4 lobular-invasive, 1 mucinous-invasive, 1 adenoid-cystic carcinoma (T1/2 in 19/1 patients, N0/1/x in 13/2/5, M0/1 in 18/2, G1/2/3 in 4/14/2, R0/x in 16/4 and L0/1/x in 15/2/3). Median tumor size was 11 mm (1-21). IORT was given with 50 kV X-rays and a single dose of 14.7-20.0 Gy (Intrabeam-System; Carl Zeiss Surgical, Oberkochen, Germany), median applicator size was 4.0 cm (2.0-5.0) and median radiation time 26.8 min (12.29-49.5). One patient had too short follow-up (F/U) and one patient had mastectomy after 2 months, for which reason 20 patients (17 breast recurrence, 3 Hodgkin's disease) were analyzed. Toxicity was assessed according to a modified LENT-SOMA scale. Results: At a median F/U of 37 months (12-91), 4 patients died (54 [lung cancer], 52 [old age], 37 [metastases], and 36 months [metastases] after IORT), 1 patient underwent mastectomy due to local relapse and contralateral secondary cancer 38 months after IORT. In total, there were 2 local relapses, 4 patients with metastases (2 before IORT, 19 and 33 months after IORT). Higher-grade fibrosis was seen in 9 cases, with a peak after 18 months. One patient developed teleangiectases, retraction and fibrosis °II. Seven patients had retraction, 57% of them in combination with fibrosis. Only 2 patients had pain, 1 hyperpigmentation, and 1 breast edema. Conclusions: IORT is feasible for treatment of in-breast tumour recurrence in previously irradiated breasts and offers an alternative to mastectomy with acceptable toxicity and good local control. No significant financial relationships to disclose.