Real-world incidence of severe myelosuppression among chronic myeloid leukemia patients treated with imatinib in Ontario

Abstract

Imatinib, approved in 2001 for the treatment of chronic myeloid leukemia (CML) based on its remarkable efficacy, was associated with severe hematologic adverse events in clinical trials. This population-based retrospective cohort study compared the incidence of severe imatinib-induced myelosuppression in 1,683 Ontario CML patients, who initiated treatment between 2002 and 2020, to the incidence reported in imatinib’s phase III randomized controlled trial (RCT). The impact of demographic factors on myelosuppression risk was evaluated among the Ontario Drug Benefit (ODB) subjects. The ODB subjects differed in demographics and had lower incidences of neutropenia and thrombocytopenia, but a higher incidence of anemia compared to RCT patients. Risk of myelosuppression increased with age, mean daily dose, and severity of comorbidities, with no difference between sexes. These results emphasize the limitations of generalizing RCT results to broader populations and the importance of continued pharmacovigilance research to better understand drug safety beyond clinical trials.