RESUMEN
PURPOSE: Breast cancer is the most common malignancy in Brazilian women, with 66,280 new cases in 2020 (with 20% overexpressing human epidermal growth factor receptor 2 [HER2]). The trastuzumab biosimilar was the first oncology biosimilar approved in Brazil for HER2-positive breast cancer treatment. This study aimed to assess the current level of knowledge of biosimilars, comfort of use, extrapolation indications, and switching of practices among oncologists in Brazil. METHODS: A 24-question survey was developed using an online platform that sought information regarding responders' characteristics and use of biosimilars. The survey analyzed the basic knowledge of biosimilars, trastuzumab biosimilars, level of comfort with extrapolation, switching treatment regimens, and opinions concerning the cost of HER2-positive breast cancer therapy. Data were collected between July and September 2019 and included 144 oncologists from five Brazilian regions. RESULTS: In total, 95% of respondents could identify the most appropriate definition of biosimilars and 96% felt comfortable prescribing trastuzumab biosimilars. Although 63% of respondents would use the biosimilar in all settings wherein the reference biologic was approved, 35% would use the biosimilar for cases involving metastatic disease. Although 82% of oncologists were in favor of switching from a reference biologic to a biosimilar, 18% would avoid switching regimens. The lack of studies detailing switching to other regimens and the correct timing to switch was the major concern. The cost of HER2 therapy was a significant concern for most oncologists. CONCLUSION: Oncologists demonstrated a high level of knowledge of biosimilars and encouraging levels of prescriber use; however, extrapolation and switching treatment regimens are barriers to the effective use of biosimilars in cancer treatment. Efforts should be concentrated on strategies involving medical education programs on biosimilars.