Assessment of racial differences in the incidence of thrombocytopenia induced by trastuzumab emtansine: a systematic review and meta-analysis

Background: Trastuzumab emtansine (T-DM1) has been proved to have value and efficacy in the treatment of advanced metastatic cancer, including in the adjuvant setting. However, there is increasing concern about T-DM1-induced thrombocytopenia (TCP), which shows racial differences in incidence. This meta-analysis aimed to evaluate differences in the incidence of T-DM1-related TCP between Asian and non-Asian patients by combining accessible information from all single-agent T-DM1 clinical trials published to date.Methods: We conducted systematic searches of the PubMed, Embase, and the Cochrane Library databases to identify relevant clinical studies of T-DM1 that reported on safety, including the incidence of TCP, which were published between January 1980 and March 2020. Two reviewers were responsible for the screening and extraction of data. The pooled-effect estimate calculated with a fixed-effects or random-effects model was represented as incidence with 95% confidence intervals (CIs).Results: A total of 29 studies involving 6,188 patients were included. The incidence of all-grade TCP in Asian patients and non-Asian patients was 0.39 (95% CI: 0.11–0.67) and 0.29 (95% CI: 0.23–0.35), respectively. The incidence of TCP of grade 3 or higher in Asians was 0.20 (95% CI: 0.10–0.29), compared with 0.02 (95% CI: 0.01–0.03) in non-Asians. Gastrointestinal cancer type and a T-DM1 treatment dose of 2.4 mg/kg Q3W were related to grade 3 or higher TCP events.Discussion: Asian patients have a higher risk of developing TCP after receiving T-DM1 than non-Asian patients. Clinicians should be aware of the importance of careful observation of platelet count in patients receiving T-DM1 therapy.