Abstract PO1-17-03: Real-world evidence of Trastuzumab biosimilars in HER2-positive breast cancer: Evaluating utilization, efficacy, and safety in Taiwan

Abstract Purpose Biosimilars have emerged as a promising alternative to reference biologic products for the treatment of cancers and immunological diseases. With regard to breast cancer, trastuzumab, a reference monoclonal antibody biologic, has been the standard of care for early and advanced HER2-positive breast cancer since 1998. Trastuzumab biosimilars, which provide comparable efficacy at a lower cost, have the potential to reduce financial burden on patients and healthcare systems and improve patient access to HER2-targeted therapy. This study aimed to evaluate the utilization, efficacy, and safety of trastuzumab biosimilars in HER2-positive breast cancer patients at Kaohsiung Veterans General Hospital. Methods A total of 113 HER2-positive breast cancer patients were enrolled between February 2020 and December 2022 and treated with trastuzumab biosimilars (OGIVRI®, trastuzumab-dkst). Of these, 44 were in the neoadjuvant group, 27 in the adjuvant group, and 42 in the metastatic group. Clinical outcomes were evaluated, including pathological complete response (pCR) rate in the neoadjuvant group, objective response rate (ORR) and clinical benefit rate (CBR) in the metastatic group, and safety profile in all groups. Results In the neoadjuvant group, 18 out of 44 evaluable patients achieved pathological complete response after surgery, resulting in a pCR rate of 40.90%. In the metastatic group , the ORR was 57.14% and the CBR was 90.47%. Furthermore, in the metastatic group, treatment with dual blockade using biosimilars resulted in an better ORR of 62.96%. No adverse events of cardiac toxicity were reported in any group. In the adjuvant group, longer follow-up is needed to assess efficacy. Conclusions Our real-world experience suggests that trastuzumab biosimilars are a safe and cost-effective alternative to reference trastuzumab in the treatment of HER2-positive breast cancer. Biosimilar trastuzumab demonstrated efficacy in the neoadjuvant setting, while dual blockade with biosimilars resulted in better disease control in the metastatic setting. Further follow-up is necessary to evaluate the efficacy of trastuzumab biosimilars in the adjuvant setting. Citation Format: Yi-Hung Lo, Yen-Dun Tzeng. Real-world evidence of Trastuzumab biosimilars in HER2-positive breast cancer: Evaluating utilization, efficacy, and safety in Taiwan abstract. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO1-17-03.