7045 Background: Venetoclax (ven) is a BCL2 inhibitor used for the treatment (tx) of chronic lymphocytic leukemia (CLL) which can cause clinical or laboratory (lab) tumor lysis syndrome (TLS). A dose ramp-up schedule and prophylaxis strategies are incorporated into NCCN guidelines and prescribing information. Prior reports have of TLS focused mostly on patients (pts) with relapsed/refractory CLL receiving ven as monotherapy. Methods: We included pts >18y who were diagnosed with CLL or small lymphocytic lymphoma (SLL) and received tx with commercial ven in any line of therapy at our institution from 1/1/2016 to 12/31/2020. TLS was defined using the modified Cairo Bishop Criteria. TLS risk was based on the size of the largest lymph node (LN) on imaging or examination and the absolute lymphocyte count (ALC) as defined by ven prescribing information. Results: We included 616 ven escalations among 136 pts with CLL. Median age was 70 years and 86% were white. Ven was part of first line of tx for 48 pts (35%). 11% had high TLS risk at baseline; 37% among those escalated exclusively inpatient (IP) and 2% among those escalated exclusively outpatient (OP). Among those treated with ven, 47 pts (35%) received ven monotherapy. 74 (54%) of pts were escalated exclusively OP, 35 (26%) had at least one prophylactic hospitalization and 27 (20%) were escalated exclusively IP. During ven initiation, 86% of pts received allopurinol, 71% intravenous hydration, 18% phosphate binders, and 10% prophylactic rasburicase. Among the entire cohort, 8 pts (5.9%) developed lab TLS and zero developed clinical TLS. There were 11 TLS events; 2 pts developed TLS in more than one escalation. Incidence of TLS was 15% for those escalated exclusively IP, 5.7% for those with any prophylactic hospitalization and 2.7% for those escalated exclusively OP. Those who developed TLS were more likely to have a higher TLS risk at baseline, preceding isolated hyperuricemia, or CrCl measurement < 60 mL/min (Table). Conclusions: In this single institution retrospective cohort study, lab TLS was observed, though clinical TLS was not. Baseline hyperuricemia and impaired renal function were more common among those who developed lab TLS compared to those who did not. Prophylactic measures, including use of IV hydration, may have contributed to low rates of observed TLS in the outpatient setting. [Table: see text]
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