(HealthDay News) — A proposed biosimilar is comparable to trastuzumab for women with ERBB2-positive metastatic breast cancer, according to a study published online Dec. 1 in the Journal of the American Medical Association.

Hope S. Rugo, M.D., from the University of California, San Francisco, Helen Diller Family Comprehensive Cancer Center, and colleagues compared the overall response rate and safety of a proposed trastuzumab biosimilar plus a taxane or trastuzumab plus a taxane in patients without prior treatment. Patients with metastatic breast cancer were randomized to a proposed biosimilar (230 patients) or trastuzumab (228 patients) with a taxane. The intention-to-treat population included 458 women, and the safety population included 493 women.

The researchers found that the overall response rate (ORR) at 24 weeks was 69.6 percent for the proposed biosimilar and 64 percent for trastuzumab; the ORR ratio and ORR difference were within the equivalence boundaries. No statistically significant difference was seen at week 48 for the proposed biosimilar versus trastuzumab for time to tumor progression, progression-free survival, or overall survival. Overall, 98.6 and 94.7 percent of the proposed biosimilar and trastuzumab groups had at least one adverse event, most commonly neutropenia (57.5 vs. 53.3 percent), peripheral neuropathy (23.1 vs. 24.8 percent), and diarrhea 20.6 vs. 20.7 percent).

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“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,” the authors write.

Several authors disclosed financial ties to the biopharmaceutical industry, including Mylan Inc. and Biocon Research Ltd., which funded the study.

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