for post-operative HDRB (Figure 1. If the final pathological report confirmed the "suitable" status for APBI, planification CT-scan was performed to deliver a 16 Gy single fraction. Clinical target volume dose constraints (CTV Z clips + 15 mm) were V100 3 95%, V150<33%, V200<12%, DNR<0.35. Organ at risk (skin, chest wall) were outlined with calculation of D0.1, D1 and D2cc and V25, V50 and V75%. Dosevolume adaptation was manually achieved by graphical optimization. Surveillance was performed at 1, 3 and 6 months after HDRB for acute toxicity analysis (CTCv4.0), quality of life (QLQ-C30V3; QLQ-BR23) and cosmetic outcome (patient and doctor point of view, photos reviewed by 2 independent radiation oncologists). Geriatric assessment was performed by the geriatric oncology team (MMSE, MNA, GDS, ADL, and IADL). Results: Median age was 77 years [69 e 89], median BMI was 26 [18 e 37] (Cup 3 C Z 54%). Median time interval between lumpectomy and HDRB was 7 days [6 e 12]. Median CTV was 46 cc [27-93] (median catheter number Z 12 [7-15], median plan number Z 2 [2 e 3]. Median V100, V150, and V200 were 97% [89-100], 33% [27-43], and 12% [9-16] respectively. Median DNR was 0.35 [0.27 e 0.43]. Median V25, V50 and V75% of the skin and the chest wall were 42, 6, 0 cc and 46, 12, 2 cc respectively. Acute toxicity was observed in 17 pts (65%) who presented 39 toxicities (G1: 31 pts (80%) mainly breast fibrosis; G2: 6 pts (15%) hematoma, pain, skin reaction; G3: 2 pts (5%) hematoma and infection. All patients who experienced acute toxicity fully recovered 6 months after HDRB. Cosmetic evaluation at 6 months was excellent/good in 90% for the patients and 99% for the doctors. Results of quality of life, independent photo review, and geriatric assessment will be presented during the ASTRO meeting. Conclusion: A single dose (HDRB) of 16 Gy delivered post-operatively for APBI suitable elderly patients appear feasible and reproducible. Acute toxicity is acceptable as well as early cosmetic outcome. Longer follow-up and larger patient cohort will be necessary to confirm those preliminary results.