Incidence and risk of tumor lysis syndrome in patients with relapsed chronic lymphocytic leukemia (CLL) treated with venetoclax in routine clinical practice.

The risk of TLS in patients with relapsed CLL treated outside of clinical trials is not well described. Using the Mayo Clinic CLL Database, 48 patients treated with venetoclax for relapsed CLL in routine practice were identified; chart review determined baseline risk for TLS and laboratory abnormalities during venetoclax ramp-up. Overall, 6 (13%) patients developed laboratory TLS, 3 of whom demonstrated clinical TLS. The majority of patients who developed TLS were stratified as low or medium risk by the package insert. Of the 42 patients who did not meet Howard criteria for TLS, isolated hyperphosphatemia occurred in 19 patients (45%), hyperkalemia in 13 patients (31%), hyperuricemia in 2 patients (5%), and hypocalcemia in 1 patient (2%). In routine practice, the incidence of TLS appears higher than reported in clinical trials (3-6%). Half of patients who did not meet criteria for TLS developed clinically significant electrolyte abnormalities that required medical intervention.