Subcutaneous Trastuzumab with Pertuzumab and Docetaxel in HER2-Positive Metastatic Breast Cancer: Final Analysis of MetaPHER, A Phase 3b Single-Arm Safety Study

Abstract

BACKGROUND Intravenous trastuzumab, pertuzumab, and docetaxel is first-line standard of care for patients with HER2-positive metastatic breast cancer. Subcutaneous trastuzumab plus intravenous pertuzumab and chemotherapy has shown similar safety and tolerability to intravenous trastuzumab in patients with HER2-positive early and metastatic breast cancer; however, in the metastatic setting, this has yet to be shown globally.METHODS In this open-label, single-arm, multicenter phase 3b study, eligible patients were ≥18 years old with histologically/cytologically confirmed previously untreated HER2-positive metastatic breast cancer. All patients received ≥1 dose of subcutaneous trastuzumab (fixed-dose 600 mg) plus intravenous pertuzumab (loading dose: 840 mg/kg; maintenance dose: 420 mg/kg) and docetaxel (≥6 cycles; initial dose 75 mg/m2) every 3 weeks. The primary objective was safety and tolerability; secondary objectives included efficacy.RESULTS At clinical cutoff, 276 patients had completed the study; median duration of follow-up was 27 months. The most common any-grade adverse events were diarrhea, alopecia, and asthenia. The most common grade ≥3 adverse events were neutropenia, febrile neutropenia, and hypertension. There were no cardiac deaths and mean left ventricular ejection fraction was stable over time. Median investigator-assessed progression-free survival was 18.7 months; objective response rate was 75.6%.CONCLUSIONS Efficacy/safety results of subcutaneous trastuzumab plus intravenous pertuzumab and docetaxel in metastatic breast cancer are consistent with historical evidence of intravenous trastuzumab. These findings further support the body of evidence indicating that subcutaneous administration does not affect the safety and efficacy profile of trastuzumab in HER2-positive breast cancer. TRIAL REGISTRATION ClinicalTrials.gov Identifier: NCT02402712 (date of registration: 30th March 2015)