Real-world incidence and prevention of tumor lysis syndrome in chronic lymphocytic leukemia treated with venetoclax

Venetoclax is a B-cell lymphoma 2 inhibitor used in chronic lymphocytic leukemia (CLL), which can cause tumor lysis syndrome (TLS). We aimed to determine the incidence of, and risk factors for, TLS among patients with CLL/small lymphocytic lymphoma who received treatment with venetoclax at our institution from 1 January 2016 to 31 December 2020. We included 616 venetoclax escalations among 136 patients with CLL. Overall, 74 patients (54%) underwent escalation exclusively outpatient, 35 (26%) had at least 1 planned hospitalization, and 27 (20%) were escalated exclusively inpatient. During venetoclax initiation, 86% of patients received allopurinol, 71% intravenous hydration, 18% phosphate binders, and 10% prophylactic rasburicase. Among the entire cohort, 7 patients (5.1%) developed laboratory TLS by modified Cairo Bishop criteria and none developed clinical TLS. Incidence of laboratory TLS was 15% for those escalated exclusively inpatient, 2.9% for those with any prophylactic hospitalization, and 2.7% for those escalated exclusively outpatient. Those who developed TLS were more likely to have higher TLS risk, and no additional risk factors were identified. In this single institution retrospective cohort study, laboratory TLS was observed, although clinical TLS was not. Prophylactic measures, including use of IV hydration, may have contributed to low rates of observed TLS in the outpatient setting.