Background: ExteNET showed that neratinib, an irreversible pan-HER tyrosine kinase inhibitor, given for 1 year after trastuzumab-based therapy significantly improved invasive disease-free survival in women with early-stage HER2-positive breast cancer. We report the final analysis of overall survival in ExteNET., Methods: In this international, randomised, double-blind, placebo-controlled, phase 3 trial, women aged 18 years or older with stage 1-3c (amended to stage 2-3c) HER2-positive breast cancer who had completed neoadjuvant and adjuvant chemotherapy plus trastuzumab were eligible. Patients were randomly assigned to oral neratinib 240 mg/day or placebo for 1 year. Randomisation was stratified according to hormone receptor (HR) status (HR-positive vs. HR-negative), nodal status (0, 1-3 or 4+), and trastuzumab regimen (sequentially vs. concurrently with chemotherapy). Overall survival was analysed by intention to treat. ExteNET is registered (Clinicaltrials.gov: NCT00878709) and is complete., Results: Between July 9, 2009, and October 24, 2011, 2840 women received neratinib (n = 1420) or placebo (n = 1420). After a median follow-up of 8.1 (IQR, 7.0-8.8) years, 127 patients (8.9%) in the neratinib group and 137 patients (9.6%) in the placebo group in the intention-to-treat population had died. Eight-year overall survival rates were 90.1% (95% CI 88.3-91.6) with neratinib and 90.2% (95% CI 88.4-91.7) with placebo (stratified hazard ratio 0.95; 95% CI 0.75-1.21; p = 0.6914)., Conclusions: Overall survival in the extended adjuvant setting was comparable for neratinib and placebo after a median follow-up of 8.1 years in women with early-stage HER2-positive breast cancer., Competing Interests: Conflict of interest statement The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: SD declares institutional grants from Puma Biotechnology Inc. during the conduct of the study, institutional grants from Pfizer, Novartis, AstraZeneca, RocheGenentech, Lilly, Myriad, Orion, Amgen, Sanofi, Genomic Health, GE, Servier, MSD, Bristol Myers Squibb, Pierre Fabre, Seagen, Exact Sciences, Rappta, Besins, European Commission, French Government, Fondation ARC, Taiho, and Elsan, and non-financial support from Pfizer, AstraZeneca, and RocheGenentech outside the submitted work. BE is a Medical Director of the Danish Breast Cancer Group, and has received a personal grant from the Danish Cancer Society, and institutional grants from Samsung Bioepis, MSD, Pfizer, and AstraZeneca. HI declares institutional grants from Chugai, Eli Lilly, Nihon Kayaku, Daiichi Sankyo, AstraZeneca, Taiho, Pfizer, MSD, Sanofi, Novartis, Bayer, and Boehringer Ingelheim, personal consulting fees from Chugai, Kyowa Hakko Kirin, AstraZeneca, Eli Lilly, Pfizer, and Daiichi Sankyo, and personal payment or honoraria for lectures, presentations, speakers bureaus, manuscript writing or educational events from Chugai, AstraZeneca, Eli Lilly, Pfizer, Taiho, Daiichi Sankyo, Eisai, and Kyowa Kirin. MG has received consulting fees from Lifebrain, Daiichi Sankyo, AstraZeneca, Eli Lilly, Veracyte, Novartis, and MSD, payment or honoraria for lectures, presentations, speakers' bureaus, manuscript writing or educational events from AstraZeneca, Eli Lilly, and Pierre Fabre, support for attending meetings and/or travel from Eli Lilly, and declares that his spouse is employed by Sandoz. MB is a stockholder of the International Drug Development Institute. CHB declares support from Puma Biotechnology for work completed for the present manuscript, institutional grants or contracts from Abbvie, Nektar, Pfizer, Polyphor, Amgen, Daiichi Sankyo, Sanofi, Exelixis, Regeneron, Novartis, Henlius, Shanghai, GSK, Janssen, OBI Pharma, Lilly, Seagen, Checkpoint Therapeutics, Roche, BMS, MSD, Merck Serono, AstraZeneca, Novocure, Aveo Oncology, Takeda, TRIO, PharmaMar, Celgene, Myovant, PPD, Syneos Health, Docs, Labcorp, ICON, IQVIA, Parexel, Nuvisan, PSI, and Medpace, advisory board or consulting fees from Boehringer Ingelheim, GSK, Novartis, Pfizer, Roche/Genentech, Eisai, Bayer, MSD, AstraZeneca, Zodiac, Lilly, Sanofi, and Daiichi Sankyo, payment or honoraria for lectures, presentations, speakers' bureaus, manuscript writing or educational events from Boehringer Ingelheim, GSK, Novartis, Pfizer, Roche/Genentech, Eisai, Bayer, MSD, AstraZeneca, Zodiac, Lilly, Sanofi, and Daiichi Sankyo, support for attending meetings and/or travel from Daiichi Sankyo, participation on a Data Safety Monitoring Board or Advisory Board for Roche/Genentech, and is a member of the BIG Executive Board. TS received payments for lectures, presentations and educational events from Novartis, Pfizer, Eli Lilly, Roche, Amgen, Sandoz, Abbot, and AstraZeneca, support for attending symposia from Novartis, Pfizer, and Roche, and received drugs for patient treatment through market access programmes from Novartis, Pfizer, and Puma Biotechnology Inc. RŠ received payment or honoraria for lectures, presentations, speakers' bureaus, manuscript writing or educational events from Pfizer, Novartis, Roche, and Astellas, and support for attending meetings and/or travel from Novartis and Roche. AGZ reports an institutional grant from Pfizer, consulting fees from AstraZeneca, Pierre Fabre, Novartis, Exact Sciences, and Lilly, payment or honoraria for lectures, presentations, speakers' bureaus, manuscript writing or educational events from Novartis, Pfizer, AstraZeneca, and Exact Sciences, support for attending meetings and/or travel from Novartis, Pfizer, and Lilly, and a leadership or fiduciary role in GEICAM. ND declares support for the present manuscript, grants or contracts from the US Oncology Network, support for attending meetings and/or travel for a Seattle Genetics advisory board, participation on a Data Safety Monitoring Board or Advisory Board for Alliance, leadership or fiduciary role at the Arlington Free Clinic, and stock or stock options with AstraZeneca (employee currently). DP declares a leadership or fiduciary role on the Board of Directors, Community Oncology Alliance. EG has received payment or honoraria for lectures, presentations, speakers' bureaus, manuscript writing or educational events from BMS, Pfizer, Roche, Novartis, AstraZeneca, Janssen, Amgen, Gilead, Lilly, Astellas, and GEN Ilac Ve Saglik Urunleri Sanayi Ve Ticaret, payment for expert testimony from BMS, Pfizer, Roche, Novartis, AstraZeneca, Amgen, Gilead, and Lilly, support for attending meetings and/or travel from BMS, Roche, Pfizer, Astellas, and Abdi Ibrahim, participation on a Data Safety Monitoring Board or Advisory Board for BMS, Pfizer, Roche, Novartis, AstraZeneca, Janssen, Amgen, Gilead, Lilly, and Astellas. IG declares funding for the trial, provision of study drug and manuscript support from Puma Biotechnology Inc., clinical trial support from Pfizer and AstraZeneca, and stock or stock options for Pfizer and Merck. SL declares institutional grants or contracts from Abbvie, AstraZeneca, Celgene, Daiichi Sankyo, Gilead, Novartis, Pfizer, and Roche, royalties or licenses paid to institution from VM Scope GmbH, payments or honoraria for lectures, presentations, speakers bureaus, manuscript writing or educational events paid to institution from AstraZeneca, Daiichi Sankyo, Gilead, Novartis, Pfizer, and Roche, patents pending and issued paid to institution (EP14153692.0, EP21152186.9, EP15702464.7, EP19808852.8), participation on Data Safety Monitoring Boards or Advisory Boards paid to institution for Abbvie, Amgen, AstraZeneca, BMS, Celgene, Daiichi Sankyo, Eirgenix, GSK, Gilead, Lilly, Merck, Novartis, Pfizer, Pierre Fabre, Roche, Sanofi, and Seagen, and medical writing (non-financial) for Daiichi Sankyo, Gilead, Novartis, Pfizer, Roche, and Seagen. NM declares grants or contracts from Chugai, Eli Lilly, Astra Zeneca, Pfizer, Daiichi Sankyo, MSD, Eisai, Novartis, Sanofi, Kyowa-Kirin, and Nippon-Kayaku, payment or honoraria for lectures, presentations, speakers bureaus, manuscript writing or educational events from Chugai, Pfizer, AstraZeneca, Eli Lilly, and Eisai, and is a representative director (unpaid) of JBCRG (Japan Breast Cancer Research Group). KP has received consulting fees from Eli Lilly, Pfizer, Novartis, Pierre Fabre, AstraZeneca, and MSD, payment or honoraria for lectures, presentations, speakers' bureaus, manuscript writing or educational events from Eli Lilly, MSD, Novartis, Pfizer, and AstraZeneca, and support for attending meetings and/or travel from Gilead. DDP is a full-time employee at Puma Biotechnology Inc., and has ownership interest (stock, stock options) in Puma Biotechnology Inc. AW is a full-time employee at Puma Biotechnology Inc., and has ownership interest (stock, stock options) in Puma Biotechnology Inc. MM declares an institutional grant from Puma Biotechnology Inc. for work completed for the present manuscript, consulting fees from Roche, Novartis, AstraZeneca, Daiichi Sankyo, Seagen, Lilly, and Sanofi, payment or honoraria for lectures, presentations, speakers' bureaus, manuscript writing or educational events from Seagen, Lilly, AstraZeneca, Pfizer, Daiichi Sankyo, and Roche, and that he is Chairman of GEICAM, and Member of Board of Directors of TRIO. All remaining authors have declared no conflicts of interest., (Copyright © 2023 The Authors. Published by Elsevier Ltd.. All rights reserved.)