209P Safety of autologous fat grafting in breast cancer: A multicenter Italian study among 17 Senonetwork Breast Units

Background: Treatment of early stage breast cancer (BC) has evolved in its multidisciplinary approach, comprising surgery, radiotherapy and oncoplastic reconstruction. Autologous fat grafting (AFG), defined as the re-implant to the breast of fat tissue from different body areas, has been firstly applied to aesthetic plastic surgery and then used in reconstructive surgery, mainly for scar correction, nipple reconstruction and opposite breast altering to achieve a balanced appearance. Nevertheless, due to the potentially unsafe stem-like properties of adipocytes at the tumoral bed level, no clear evidence of the procedure’s safety, in terms of oncological relapse, has been clearly documented so far. Methods: We retrospectively collected data of early BC patients from 17 Italian Breast Units, followed from January 1997 to March 2018, and assessed differences in terms of locoregional recurrence rate (LRR) and locoregional recurrence-free survival (LRFS) between patients who underwent AFG and patients who did not. The primary endpoint of the study was equivalence of LRR, between AFG and non-AFG groups. A LR difference within 5%, with a bilateral alpha error of 5% and 80% power was considered as equivalent. Differences were analyzed in the entire cohort of invasive tumors and in different subgroups, according to prognostic biological subtypes. Results: Among the 6703 evaluable invasive BC, 2227 (33.2%) underwent AFG procedure and 4476 (66.8%) did not. With a median follow-up time of 65 months, LRR was 5.3% in the global population, 4.4% in the AFG group and 5.7% in the non-AFG group, suggesting no difference between the two groups (p¼0.021, HR 0.65, 95% CI 0.51-0.82). No significant differences in terms of LRFS were also documented among different biological subtypes (luminal-like group, HR 0.50, 95% CI 0.29-0.87, p¼0.015; luminal HER2, HR 0.19, 95% CI 0.04-0.83, p¼0.027; HER2 enriched-like, HR 0.61, 95% CI 0.12-3.02, p¼0.544; and TNBC, HR 0.02, 95% CI 0.005-0.12, p<0.001). Conclusions: Our study consolidates previous data on AFG oncological safety, confirming, in a very large, multicenter cohort of early BC patients that, besides the wellknown benefits on the aesthetic result, AFG does not interfere negatively on cancer prognosis.