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Aim: The Cher-LOB randomised phase II study showed that the combination of lapatinib-trastuzumab plus chemotherapy increases pathologic complete response (pCR) rate compared with chemotherapy plus either trastuzumab or lapatinib. Here, we report the post hoc survival analysis as per treatment arm, pCR and biomarkers., Methods: The Cher-LOB study randomised 121 patients with human epidermal growth factor receptor 2-positive, stage II-IIIA breast cancer. A specific protocol to collect recurrence-free survival (RFS) and overall survival (OS) data was designed. Tumour-infiltrating lymphocytes (TILs) and PAM50-intrinsic subtyping were evaluated at baseline., Results: At 9-year median follow-up, a trend towards RFS improvement with lapatinib-trastuzumab over trastuzumab was observed (hazard ratio [HR] 0.44, 95% confidence interval [CI] 0.18-1.05). Combining treatment arms, pCR was significantly associated with both RFS (HR 0.12, 95% CI 0.03-0.49) and OS (HR 0.12, 95% CI 0.03-0.49). TILs were significantly associated with RFS (HR = 0.978 for each 1% increment). Luminal-A subtype was a significant and independent predictor of improved RFS as compared with other PAM50-based intrinsic subtypes at the multivariate analysis including the most relevant clinicopathologic variables (HR 0.29, 95% CI 0.09-0.94, p = 0.040)., Conclusions: Cher-LOB trial survival analysis confirmed the prognostic role of pCR and TILs and showed a signal for a better outcome with lapatinib-trastuzumab over trastuzumab., Trial Registration: NCT00429299., Competing Interests: Conflict of interest statement V.G. reports personal fees from Roche, Novartis, Eli Lilly and MSD outside the submitted work. D.G.G. reports personal fees from Roche, Novartis, Eli Lilly and Pierre Fabre, all outside the submitted work. A.F. reports personal fees from Roche, Novartis, Pfizer, Lilly, Daiichi and Seagen, all outside the submitted work. L.G. reports honoraria for lectures and ad boards from Lilly, Pfizer, Novartis and AstraZeneca, all outside the submitted work, reports travel accommodation and expenses from Novartis and Daiichi Sankyo and is an uncompensated member of the Olympia steering committee. A.M. reports grants and personal fees from Roche and Eisai; personal fees from Lilly, MacroGenics and Novartis and grants from Pfizer, all outside the submitted work. S.C. reports personal fees from Lilly Oncology outside the submitted work. A.P. reports grants and personal fees from Roche, AstraZeneca, Daiichi Sankyo, Merck Sharp & Dohme (MSD), PUMA Biotechnology, Novartis and Nanostring Technologies, personal fees from Seattle Genetics, Lilly, Pfizer, Guardant Health, Oncolytics Biotech and Abbvie, all outside the submitted work, and a patent (WO2018/103834A1) licensed to Nanostring Technologies, a patent (WO/2018/096191) issued. M.V.D. reports personal fees from Lilly, Genomic Health, Novartis and Celgene, all outside the submitted work. P.F.C. reports personal fees from Novartis, Eli Lilly, AstraZeneca, Tesaro, BMS and Roche, all outside the submitted work. All remaining authors have declared no conflicts of interest., (Copyright © 2021 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Lapatinib enhances antibody-dependent cell-mediated cytotoxicity (ADCC) activity of trastuzumab. FcγR polymorphisms have been associated with both ADCC and clinical activity of trastuzumab in HER2+ breast cancer (BC) patients (pts). We analyzed FcγRIIa-H131R and FcγRIIIa-V158F polymorphisms in the CHER-LOB trial population of HER2+ BCs treated with preoperative chemotherapy plus trastuzumab (arm A), lapatinib (arm B) or both (arm C). Genotyping was successfully performed in 73/121 (60%) pts. A significant improvement in pathological complete response (pCR) rate was observed for the combination arm C, but only in FcγRIIIa V allele carriers (C vs A, 67 vs 27%, P=0.043; C vs B, 67 vs 22%, P=0.012). An independent interaction between arm C and FcγRIIIa V allele was found for pCR (odds ratio=9.4; 95% confidence interval, 2.3-39.6; P=0.003). No significant associations were observed between pCR and FcγRIIa polymorphism, and between pre-treatment tumor-infiltrating lymphocytes and FcγR polymorphisms. Our study provides evidence for a FcγRIIIa V allele-restricted pCR benefit from neoadjuvant trastuzumab plus lapatinib in HER2+ BC.