Infusion Reactions in HER2-Positive Gastric Cancer: Switching from Trastuzumab to Its Biosimilar

This study presents a safety analysis of infusion reactions (IRs) in gastric cancer patients who switched from reference trastuzumab to its biosimilar, trastuzumab-NK, at the Saitama Cancer Center in Japan from April 2018 to March 2022. IRs were identified if patients developed symptoms such as fever, chills, infusion-related reactions, hypersensitivity, rash, pruritus, urticaria, systemic disorders, or immune system disorders on the day of administration or the following day. The incidence of IRs was 14% in the reference trastuzumab group, 33% in the trastuzumab-NK group, and 33% in the switching group. There was no significant difference in IR incidence between the reference trastuzumab and trastuzumab-NK groups (p = 0.235). Among the switching group, only one of the three patients who experienced an IR had a reaction associated with the switch. These findings suggest that the frequency of IRs in the switching group gastric cancer is comparable to the other groups, indicating that switching is a viable treatment option with appropriate management. Additionally, 37 of the 45 patients in the study were male, provides new safety information on switching in gastric cancer for male patients that has not been previously reported.