A Retrospective analysis of biosimilar and reference trastuzumab in human epidermal growth factor receptor-2 positive early and/or locally advanced breast cancer patients treated with neoadjuvant-adjuvant setting: Safety and event-free survival outcomes

Background: There is limited real-world evidence on the treatment outcomes with Trastuzumab, specifically with biosimilars. This analysis aims to evaluate the safety and effectiveness of Trastuzumab in early and/or locally advanced breast cancer patients treated with neoadjuvant-adjuvant treatment in the real world setting and to compare biosimilar with reference trastuzumab. Materials and Methods: We retrospectively analyzed the data of patients with human epidermal growth factor receptor-2 (HER-2)-positive breast cancers, who were treated with trastuzumab-based standard therapies. The survival curves were generated using the Kaplan–Meier method. Event-free survival (EFS) was calculated. All patients were assessed for toxicity as per CTCAE version 4.0. The subgroup analysis was carried out to compare the effectiveness of biosimilar with reference trastuzumab. Results: A total of 88 patients were evaluated from 2008 to 2018. EFS at 1, 2, and 5-year was 89.5%, 78%, and 44.2%, respectively. The median EFS was 43 months. In subgroup analysis, the 1, 2-, and 3-year EFS rates were 86.7%, 86.7%, and 57.8%, respectively, for reference Trastuzumab (n = 29) as compared to 91%, 74.4%, and 56.9%, respectively, for Biosimilar Trastuzumab (n = 59). Similarly, median EFS was 43 months and not reached, respectively. There was no significant difference in EFS between the two groups (P = 0.991). A significant asymptomatic decrease in the left ventricular ejection fraction (LVEF) of ≥10% to below the lower limit of normal was noted in only two patients (2.3%). There was no significant difference observed in reduction of LVEF to below the lower limit of normal between the two groups (P = 0.514). The common grade 3/4 adverse events (AEs) observed such as vomiting, diarrhea, pancytopenia, and anemia were mostly due to chemotherapy. These AEs were comparable in both groups. Conclusions: The EFS in our study is consistent with the historical data. Safety and effectiveness of biosimilars were comparable to the reference transtuzumab.