Trastuzumab Biosimilar Has Similar Efficacy, Safety to Reference Product in Advanced Gastric Cancer

Herzuma, a trastuzumab biosimilar, has equivalent outcomes and similar safety compared with reference trastuzumab (Herceptin) in HER2-positive advanced gastric cancer (AGC), according to a study published in American Journal of Clinical Oncology.

Researchers evaluated the medical records of 102 patients with HER2-positive AGC who were treated with first-line trastuzumab-based chemotherapy between February 2011 and December 2020 at the Gachon University Gil Medical Center in the Republic of Korea. A total of 72 patients received reference trastuzumab and 30 patients received the biosimilar.

The addition of trastuzumab to chemotherapy has significantly improved overall survival among patients with HER2-positive AGC compared with chemotherapy alone. However, trastuzumab and other targeted cancer drugs are more expensive than chemotherapy.

“Despite its clinical benefits, this high price can represent a substantial barrier to trastuzumab treatment, especially in a financially constrained environment,” the authors wrote. “Since the price of biosimilars is generally lower than that of the reference products, the cost saved by switching patients to biosimilars could enable improved access to these clinically effective drugs.”

The baseline characteristics of the patients in both groups were largely similar. However, patients receiving reference trastuzumab had better Eastern Cooperative Oncology Group performance status (ECOG PS) than those in the biosimilar group: 29.2% of the reference group vs 6.7% of the biosimilar group had ECOG PS 0, 54.2% of the reference group had ECOG PS 1 vs 73.3% of the biosimilar group, and 16.7% of the reference group had ECOG PS 2 vs 20.0% of the biosimilar group.

The researchers found:

• The objective response rate of the groups was similar (52.8% for reference vs 56.7% for biosimilar)
• Only 2 patients receiving the reference achieved a complete response, but no patients in the biosimilar group achieved it (P = .720)
• For the reference group, the disease control rate was 69.4% compared with 73.3% for the biosimilar group (P = .695)

The median follow-up was 48.0 months for the reference group and 7.2 months for the biosimilar group. After that time, 64 patients (91.4%) in the reference group and 17 patients (53.1%) in the biosimilar group had progressed or died. In the reference group, median progression-free survival was 6.9 months compared with 5.4 months in the biosimilar group. The median overall survival was not reached in the biosimilar group and was 12.3 months in the reference group.

The most frequent adverse events in both groups were hematological toxicities. While 12.5% of patients in the reference group and 10.0% in the biosimilar group reported heart failure, there were no reports of grade 3 or 4 heart failure.

“The results of this study demonstrated similar clinical efficacy and safety between the biosimilar trastuzumab and its reference product in patients with HER2-positive AGC,” the authors wrote. “To the best of our knowledge, this study is the first to directly compare the efficacy and safety of trastuzumab biosimilar to reference trastuzumab in patients with AGC.”

Among the limitations of the study that authors noted were that it was a retrospective analysis based on chart review, which may miss some adverse events that were not reported, and the study population was relatively small and from a single institution.

Although larger prospective studies are needed, “this study will help investigators in planning clinical studies in patients treated with biosimilar trastuzumab,” the authors concluded.

Reference

Park J-W, Yeo JH, Kim YS, et al. Efficacy and safety of trastuzumab biosimilar (CT-P6) compared with reference trastuzumab in patients with HER2-positive advanced gastric cancer: a retrospective analysis. Am J Clin Oncol. Published online January 6, 2022. doi:10.1097/COC.0000000000000887