The objective of this real–world study was to describe characteristics, treatment patterns, and reasons for treatment discontinuation among patients with chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL) who discontinued acalabrutinib and subsequently initiated zanubrutinib in a community oncology setting.

A retrospective cohort was identified using the IntegraConnect PrecisionQ database, which includes electronic health records from more than three million de–identified cancer patients across over 500 care sites in the United States. Patients with CLL/SLL who initiated and discontinued acalabrutinib and then initiated zanubrutinib between November 21, 2019, and November 30, 2024, were included and followed through February 28, 2025. Medical record review was used to identify treatment initiation and discontinuation dates and reasons for discontinuation for both therapies.

Among 806 patients who initiated acalabrutinib and subsequently received another therapy, 121 later received zanubrutinib; 102 patients (84.3%) switched directly from acalabrutinib to zanubrutinib. Most patients had received acalabrutinib monotherapy (91.7%), with 72.6% receiving it as first–line therapy. Median duration of acalabrutinib prior to zanubrutinib was 5.6 months (IQR, 2.1–16.5), and 66.7% discontinued acalabrutinib within one year, primarily due to toxicity (68.6%). Median duration of zanubrutinib was 10.7 months (IQR, 4.1–18.8), with 57.8% remaining on treatment at data cutoff. Among patients who discontinued zanubrutinib, toxicity was the most commonly reported reason (58.1%), followed by other reasons (7.0%) and disease progression (2.3%).