Abstract Background: As biosimilars and subcutaneous (SQ) formulations of intravenous (IV) biologics enter the market, it is unclear how prescribers determine which formulation to give a patient. While patients may generally prefer SQ administration, IV biosimilars may be less expensive than newer SQ formulations. We focused on trastuzumab, which has name-brand SQ, name-brand IV, and biosimilar IV formulations, to assess potential association of patient and oncologist factors with drug choice and administration route. Methods: This cross-sectional study included patients with HER2+ breast or gastrointestinal (GI) cancer who received trastuzumab at the UChicago from 1/1/2021 to 12/31/2024. Patient factors, trastuzumab formulation and administration route, and prescriber were extracted from the electronic medical record. Prescriber demographics were obtained using public data from the Centers for Medicare Part 1 (Regular Abstracts); 2026 Apr 17-22; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2026;86(7 Suppl):Abstract nr 939.
Hsu et al. (Fri,) studied this question.