Abstract
Background The trastuzumab biosimilar MYL-1401O has demonstrated equivalent efficacy and comparable safety to reference trastuzumab (RTZ) in clinical trials of human epidermal growth factor receptor 2 (HER2)-positive metastatic breast cancer (MBC) as non-dual HER2 therapy. Here, we present the first real-world comparison of MYL-1401O versus RTZ with single/dual HER2-targeted therapy for the neoadjuvant, adjuvan and palliative first-/second-line treatment with HER2-positive early breast cancer (EBC) and metastatic breast cancer (MBC) patients in two tertiary hospitals in Turkey. Methods We retrospectively investigated medical records in the Severance Breast Cancer Registry in Turkey. We identified patients with HER2-positive EBC (n=159) who had received neoadjuvant chemotherapy (n= 92) with RTZ or MYL-1401O±pertuzumab and adjuvant chemotherapy (n=67) with RTZ or MYL-1401O plus taxan between january 2018 and jun 2021. Stage IV MBC (n=53) who had received palliative first-line treatment with RTZ or MYL-1401O, and docetaxel±pertuzumab (THP) or second-line treatment with RTZ or MYL-1401O, and taxan between january 2018 and jun 2021. Primary endpoints were pathological complete response in neoadjuvant grup (pCR) and progression-free survival (PFS) in adjuvant and metastatic grup. Secondary endpoints in the metastatic patient group (MBC) was overall response rate (ORR), disease control rate (DCR) and cardiac safety. Results The rate of achieving pCR in the group receiving neoadjuvant chemotherapy was similar between MYL and RTZ (62.7% [37/59] and 55.9% [19/34] p=0.509). Median PFS similar in EBC-adjuvant group, 12-24-36 months PFS respectively 96.3%, 84.7%, 71.5% in patients with MYL and 100%, 88.5%, 64.8% in patients with RTZ (95% CI p=0.577). Median PFS similar in metastatic group, 23.0 (9.8-16.1) months in patients with MYL-1401O and 23 (19.9-26.0) months in patients with RTZ (95% CI p=0.270). The ORR, DCR, and cardiac safety profiles did not also show significant difference efficacy outcomes between two groups. Conclusion These real-world data suggest that biosimilar trastuzumab MYL-1401O has similar effectiveness and cardiac safety to RTZ in HER2-positive EBC and MBC patients when administered as part of single/dual HER2-targeted therapy with chemotherapy in the neoadjuvant, adjuvant or palliative setting.