• Hope S Rugo, Abhijit Barve, Cornelius F Waller, Miguel Hernandez-Bronchud, Jay Herson, Jinyu Yuan, Rajiv Sharma, Mark Baczkowski, Mudgal Kothekar, Subramanian Loganathan, Alexey Manikhas, Igor Bondarenko, Guzel Mukhametshina, Gia Nemsadze, Joseph D Parra, Maria Luisa T Abesamis-Tiambeng, Kakhaber Baramidze, Charuwan Akewanlop, Ihor Vynnychenko, Virote Sriuranpong, Gopichand Mamillapalli, Sirshendu Ray, Eduardo P Yanez Ruiz, Eduardo Pennella, and Heritage Study Investigators.
• University of California San Francisco Helen Diller Family Comprehensive Cancer Center, San Francisco.
• JAMA. 2017 Jan 3; 317 (1): 37-47.

ImportanceTreatment with the anti-ERBB2 humanized monoclonal antibody trastuzumab and chemotherapy significantly improves outcome in patients with ERBB2 (HER2)-positive metastatic breast cancer; a clinically effective biosimilar may help increase access to this therapy.ObjectiveTo compare the overall response rate and assess the safety of a proposed trastuzumab biosimilar plus a taxane or trastuzumab plus a taxane in patients without prior treatment for ERBB2-positive metastatic breast cancer.Design, Setting, And ParticipantsMulticenter, double-blind, randomized, parallel-group, phase 3 equivalence study in patients with metastatic breast cancer. From December 2012 to August 2015, 500 patients were randomized 1:1 to receive a proposed biosimilar or trastuzumab plus a taxane. Chemotherapy was administered for at least 24 weeks followed by antibody alone until unacceptable toxic effects or disease progression occurred.InterventionsProposed biosimilar (n = 230) or trastuzumab (n = 228) with a taxane.Main Outcomes And MeasuresThe primary outcome was week 24 overall response rate (ORR) defined as complete or partial response. Equivalence boundaries were 0.81 to 1.24 with a 90% CI for ORR ratio (proposed biosimilar/trastuzumab) and -15% to 15% with a 95% CI for ORR difference. Secondary outcome measures included time to tumor progression, progression-free and overall survival at week 48, and adverse events.ResultsAmong 500 women randomized, the intention-to-treat population included 458 women (mean [SD] age, 53.6 [11.11] years) and the safety population included 493 women. The ORR was 69.6% (95% CI, 63.62%-75.51%) for the proposed biosimilar vs 64.0% (95% CI, 57.81%-70.26%) for trastuzumab. The ORR ratio (1.09; 90% CI, 0.974-1.211) and ORR difference (5.53; 95% CI, -3.08 to 14.04) were within the equivalence boundaries. At week 48, there was no statistically significant difference with the proposed biosimilar vs trastuzumab for time to tumor progression (41.3% vs 43.0%; -1.7%; 95% CI, -11.1% to 6.9%), progression-free survival (44.3% vs 44.7%; -0.4%; 95% CI, -9.4% to 8.7%), or overall survival (89.1% vs 85.1%; 4.0%; 95% CI, -2.1% to 10.3%). In the proposed biosimilar and trastuzumab groups, 239 (98.6%) and 233 (94.7%) had at least 1 adverse event, the most common including neutropenia (57.5% vs 53.3%), peripheral neuropathy (23.1% vs 24.8%), and diarrhea (20.6% vs 20.7%).Conclusions And RelevanceAmong women with ERBB2-positive metastatic breast cancer receiving taxanes, the use of a proposed trastuzumab biosimilar compared with trastuzumab resulted in an equivalent overall response rate at 24 weeks. Further study is needed to assess safety and long-term clinical outcome.Trial Registrationclinicaltrials.gov Identifier: NCT02472964; EudraCT Identifier: 2011-001965-42.

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