Treatment 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. OBJECTIVE To 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 PARTICIPANTS Multicenter, 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. INTERVENTIONS Proposed biosimilar (n = 230) or trastuzumab (n = 228) with a taxane. MAIN OUTCOMES AND MEASURES The 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. RESULTS Among 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 RELEVANCE Among 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.

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NCT01401166.

Clinical trials frequently include multiple end points that mature at different times. The initial report, typically based on the primary end point, may be published when key planned co-primary or secondary analyses are not yet available. Clinical Trial Updates provide an opportunity to disseminate additional results from studies, published in JCO or elsewhere, for which the primary end point has already been reported. PURPOSE The phase III ADAURA (ClinicalTrials.gov identifier: NCT02511106 ) primary analysis demonstrated a clinically significant disease-free survival (DFS) benefit with adjuvant osimertinib versus placebo in EGFR-mutated stage IB-IIIA non–small-cell lung cancer (NSCLC) after complete tumor resection (DFS hazard ratio [HR], 0.20 [99.12% CI, 0.14 to 0.30]; P < .001). We report an updated exploratory analysis of final DFS data. METHODS Overall, 682 patients with stage IB-IIIA (American Joint Committee on Cancer/Union for International Cancer Control, seventh edition) EGFR-mutated (exon 19 deletion/L858R) NSCLC were randomly assigned 1:1 (stratified by stage, mutational status, and race) to receive osimertinib 80 mg once-daily or placebo for 3 years. The primary end point was DFS by investigator assessment in stage II-IIIA disease analyzed by stratified log-rank test; following early reporting of statistical significance in DFS, no further formal statistical testing was planned. Secondary end points included DFS in stage IB-IIIA, overall survival, and safety. Patterns of recurrence and CNS DFS were prespecified exploratory end points. RESULTS At data cutoff (April 11, 2022), in stage II-IIIA disease, median follow-up was 44.2 months (osimertinib) and 19.6 months (placebo); the DFS HR was 0.23 (95% CI, 0.18 to 0.30); 4-year DFS rate was 70% (osimertinib) and 29% (placebo). In the overall population, DFS HR was 0.27 (95% CI, 0.21 to 0.34); 4-year DFS rate was 73% (osimertinib) and 38% (placebo). Fewer patients treated with osimertinib had local/regional and distant recurrence versus placebo. CNS DFS HR in stage II-IIIA was 0.24 (95% CI, 0.14 to 0.42). The long-term safety profile of osimertinib was consistent with the primary analysis. CONCLUSION These updated data demonstrate prolonged DFS benefit over placebo, reduced risk of local and distant recurrence, improved CNS DFS, and a consistent safety profile, supporting the efficacy of adjuvant osimertinib in resected EGFR-mutated NSCLC.

clinicaltrials.gov Identifier: NCT01514188.