• Benedetta Conte, Alessandra Fabi, Francesca Poggio, Eva Blondeaux, Chiara Dellepiane, Alessia D'Alonzo, Giuseppe Buono, Grazia Arpino, Valentina Magri, Giuseppe Naso, Daniele Presti, Silvia Mura, Andrea Fontana, Francesco Cognetti, Chiara Molinelli, Simona Pastorino, Claudia Bighin, Loredana Miglietta, Francesco Boccardo, Matteo Lambertini, Lucia Del Mastro, and Gruppo Italiano Mammella (GIM) study group.
• Department of Medical Oncology, Ospedale Policlinico San Martino, University of Genova, Genoa, Italy. Electronic address: bntconte@gmail.com.
• Clin. Breast Cancer. 2020 Apr 1; 20 (2): e181-e187.

BackgroundT-DM1 improves progression-free survival (PFS) and overall survival (OS) in patients with metastatic human epidermal growth factor receptor 2-positive (HER2+) breast cancer progressing on prior trastuzumab plus a taxane. A paucity of data is available on T-DM1 efficacy after dual anti-HER2 blockade with pertuzumab and trastuzumab plus a taxane, which represents the current first-line standard of care. The present study is a retrospective/prospective evaluation of the efficacy and activity of second-line T-DM1 after front-line pertuzumab-based therapy.Patients And MethodsEligible patients were identified within the Gruppo Italiano Mammella (GIM) 14/BIOMETA study, a retrospective/prospective multicenter study on treatment patterns and outcomes of patients with metastatic breast cancer (ClinicalTrials.gov Identifier: NCT02284581). We searched for patients who received second-line T-DM1 after taxane plus trastuzumab and pertuzumab between November 15, 2013 and May 31, 2018. We calculated median PFS, median time to treatment failure (TTF), prolonged duration of therapy (PDT), objective response rate (ORR), and 1-year OS.ResultsOf 445 patients with HER2+ metastatic breast cancer, 77 were eligible for the analysis. At a median follow-up of 7 months, median PFS was 6.3 months (95% confidence intervals [CI], 4.8-7.7 months), and median TTF was 6.2 months (95% CI, 4-8.6 months). More than one-third of patients (37.6%; n = 29) experienced PDT with an ORR of 27.1%. At data cutoff, the median OS was not reached, and the 1-year OS was 82%.ConclusionsOur results show meaningful activity of T-DM1 after front-line pertuzumab plus trastuzumab and a taxane, with about 27% of patients having an objective response and 40% of patients achieving durable disease control.Copyright © 2019. Published by Elsevier Inc.

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