241PResidual cancer burden as a prognostic factor in a large series of neoadjuvant chemotherapy. Subgroup analysis per molecular surrogated subtypes

Abstract Background Neoadjuvant chemotherapy offers the possibility to test chemo sensitivity in vivo. pCR is a good surrogate of survival. Other measures of pathological response include de residual cancer burden (RCB). The aim of our study is to assess prognostic factors of survival including RCB. Methods 488 breast cancer (BC) patients treated with NATC based on anthracyclines and taxanes with trastuzumab in HER-2 positive between 2009 and 2016 at a single Institution. Chi-square test was run for the univariate analyses and a cox-regression was performed regarding prognostic factors. Survival was calculated with Kaplan-Meier survival plots since the start of NATC to the first documented disease recurrence (DDFS) or overall survival (OS) by using IBM SPSS version 23. Results Mean age was 51.13 (24-84). After a follow up of 63 (4-129) months there have been 14 (2.9%) local recurrences; 55 (11.3%) distant recurrences and 56 deaths (11.4%), 50 due to BC progression (10.2%). In the univariate analyses those factors related to distant recurrence were histology ductal vs lobular: 14.2 vs 35.7%, p: 0.032; molecular subtype: luminal A (15.2%) vs luminal B (14.2%) vs luminal B Her2 (11.8%) vs HER2 enriched (7.7%) vs triple negative (TN) (22.8%), p: 0.042; TstageT0 (0%), T1(12.5%), T2(12.3%), T3 (18.8%) and T4 (23.9%), p: 0.006; N stage N0 (9.6); N1 (12.8), N2 (17.5) and N3(27.3%), p = 0.063;pTstage pT0 (8.5%), pTis (9.7) pT1a+b(7.5%)pT1c(20.3 %), pT2(21.8%), pT3 (29.2%) and pT4 (100%), p = 0.000; pN stage pN0 (8.2); pN1mic (0%), pN1 (16.8), pN2 (32.2) and pN3(42.3%), p = 0.000 and the RCB 0 (3.2%) vs I (7.1%) vs II (16.5%) vs III (23.4%), p: 0.0001. The estimated 5y DDFS was for RCB0: 100%; RCBI: 98%; RCBII: 85% and RCBIII: 68%. The HR for RCB was 1.4 (95%IC, 1.2-1.6), per subgroups the log rank was for luminal A: 3.4, p: 0.330; for luminal B: 10.6, p: 0.03; for luminal B Her2: 7.9, p: 0.04; for Her2 enriched: 25, p: 0.000 and for TN 16, p: 0.003. Conclusions In our large series the RCB is reproducible as a surrogate of survival special in those chemo sensitive tumors such as Her2 and triple negative ones. Legal entity responsible for the study The authors. Funding Has not received any funding. Disclosure All authors have declared no conflicts of interest.