The importance of real-world data in evaluating the safety of biosimilars: a descriptive study of clinical practice in an oncohematological population.

Background Safety concerns are often raised when switching from reference to biosimilar products and between different biosimilars. Objective The objective of this multicenter observational study is to provide an objective and representative Italian-level picture of RTX use in individuals with oncohematologic diseases during the period 2018-2022. Results 505 patients naïve to RTX treatment with NHL (n=453), CLL (n=33) or one of the diseases included in the list of Law 648/96 (n=19) were analyzed. Patients, 42% women, had a median age at baseline of 66.8 years (IQR 57.5-73.9 years); median follow-up of patients was 311 days (IQR 217-461 days). During the study period, patients received 3,681 infusions of RTX; the median number of infusions per patient was 7.3 (standard deviations 3.8). The majority of patients started therapy with the biosimilars Tru (n=298) and Rix (n=139), followed by the originator Mabiv (n=64). Seventy-eight percent (n=392) of patients did not switch during the study period, 98% of whom continued treatment with the same biosimilar (n=257) with Tru and n=130 with Rix). Those who did switch were 22% (n=113), most of whom switched from intravenous RTX to Mabsc (n=75, 67%). Conclusions This study describes the use of RTX in real clinical practice of Italian oncohematology centers. The results show that patients with switch are the minority (22%), while most remain on treatment with Rix and Tru biosimilars. Our shared approach has increased clinicians and patients confidence in biosimilars with respect to efficacy and safety, generating at the same time significant cost savings.