Real-world incidence of venetoclax toxicities in British Columbia.

Venetoclax is used to treat relapsed/refractory chronic lymphocytic leukemia (r/r CLL). Tumour lysis syndrome (TLS) is a serious toxicity associated with venetoclax, and real-world studies suggest that the incidence may be higher than in clinical trials. The purpose of this study is to describe the incidence of venetoclax toxicities in British Columbia (BC). Retrospective review of electronic medical charts for patient characteristics and clinical outcomes of patients treated with venetoclax for r/r CLL in BC. Patients were classified according to their risk for developing TLS. The incidence of TLS was categorized based on laboratory metrics or clinical diagnosis. Other non-TLS toxicities were also collected. Of 33 patients identified, 40%, 33%, and 27% were at low, intermediate, and high risk for TLS, respectively. Laboratory TLS occurred in 1/33 patients (3%), and no clinical TLS was reported. Grade 3 or 4 toxicities occurred in 19/33 patients (58%). Of these, neutropenia was the most common, occurring in 16 patients (84%) followed by thrombocytopenia, which occurred in 8 patients (42%). The incidence of TLS in patients treated with venetoclax for r/r CLL in BC was lower than in other real-world studies. Findings may warrant further investigation to determine if the higher incidence of TLS in real-world reports may be mitigated through modifying TLS risk categorization and associated prophylactic measures. Neutropenia was the most common grade 3 or 4 venetoclax toxicity reported, and the incidence in BC is comparable to other centres.