300POutcome of triple negative inflammatory breast cancers (TNIBC) treated with dose dense neoadjuvant epirubicin cyclophosphmide, prognostic impact of pre and post neoadjuvant chemotherapy (NAC) tumour infiltrating lymphocytes (TIL) and post NAC lymphovascular invasion

Abstract Background Inflammatory breast cancers (IBC) particularly triple negative (TN) subtype have poor prognosis. Methods Between January 2010 and December 2016, all patients with TNIBC seen at breast cancer disease center, St Louis hospital, Paris, France, were treated with neoadjuvant dose dense Cyclophophamide (1.2g/m2 d1) - Epirubicin (75mg/m2 d1) q2w (SIM regimen) followed with 12 injections of paclitaxel (80 mg/m2) qw or 4 injections of docetaxel (100 mg/m2) q3w. All patients have histologically proven TN tumors and no evidence of metastases. Mastectomy and axillary clearance was performed after chemotherapy. pCR was defined as no residual invasive tumor in breast and lymph nodes. TIL and lymphovascular invasion were evaluated pre and post NAC by 2 independent anatomopathologists dedicated to breast cancer. Delta TIL was defined as the difference between post chemotherapy and pre chemotherapy TIL. Results Thirty TNIBC patients were treated, 28 underwent surgery and 2 progressed during chemotherapy. Median follow-up was 45 months (8 – 103). 9/30 patients (30%) achieved pCR. Median disease free survival was not reached. Median TIL infiltration at diagnosis was 11% (0-60) and dropped to 1% after chemotherapy (0 – 80). On univariate analysis, LVI after chemotherapy (HR = 2.1 [95% CI, 1.1–3.6], p = 0.02), TIL on mastectomy (HR = 1.8 [95% CI, 1.1–3.1], p = 0.03), delta TIL (HR = 2.2 [95% CI, 1.4–3.5], p = 0,001) were associated with DFS but no pCR (p = 0,051). On multivariate analysis, only delta TIL remainedstatistically significant (HR = 1.9 [95% CI, 1.1–3.4], p = 0.03). Conclusions We showed in this retrospective series of 30 TNIBC that dose dense dose intense chemotherapy is efficient in this population. Delta TIL is a strong prognostic factor associated with DFS. We show that a positive Delta TILis, among others, a strong and independent predictor of DFS: in TNIBC contrary to the results obtained in TN non inflammatory breast cancers, an increase in TIL after chemotherapy is associated with a decrease in DFS.The exact impact of LVI must be further investigated. Legal entity responsible for the study The authors. Funding Has not received any funding. Disclosure All authors have declared no conflicts of interest.