Bruton's tyrosine kinase inhibitor zanubrutinib-based regimens in relapsed/refractory primary diffuse large B-cell lymphoma of central nervous system.

30 Background: Patients with relapsed/refractory primary central nervous system lymphoma (R/R PCNSL) usually have a poor prognosis. Ibrutinib-based regimens revealed promising efficacy but showed off-target effects and drug resistance in some cases. Here, we conducted a retrospective study to evaluate the efficacy and safety of regimens based on second-generation bruton's tyrosine kinase (BTK) inhibitor zanubrutinib in R/R PCNSL. Methods: We respectively reviewed 23 patients with R/R PCNSL treated with zanubrutinib in our center from Apr. 2021 to Jan. 2024. The primary end points were overall response rate (ORR) and progression-free survival (PFS). Secondary end points included complete response rate (CRR), disease control rate (DCR), overall survival (OS) and adverse events (AEs). Response was assessed according to International Primary CNS Lymphoma Collaborative Group criteria. The severity of AEs was graded using the NCI Common Toxicity Criteria, version 5.0. Validated next-generation sequencing (NGS) panels were used to analyze the mutational status of the BCR pathway genes or other solid tumor-related genes. Results: The median follow-up at the cutoff date (15 Jan 2024) was 17.0 months (range, 2-33 months). The ORR, CRR and DCR were 78.3%, 39.1% and 91.3%. The median PFS was 31.0 months, but the median OS was not reached. Compared to germinal center B-cell like (GCB) group, non-GCB group showed a better ORR (76.9% vs 66.7%) and CRR (46.2% VS 33.3%). Multivariate analysis revealed that overall response (vs. no response, HR=0.20, P=0.027), long duration of zanubrutinib (≥6months vs. 2-5 months, HR=0.07, P=0.009) and refractory disease status (vs. relapse disease status, HR=0.12, P=0.014) were independent factors for longer PFS. The most commonly mutated genes are MYD88(15/17,88.2%), PIM1(9/17 52.9%), CD79B (8/17,47.1%), ETV6(7/17,41.2%), BTG1(5/17,29.4%) and GNA13(5/17,29.41%). The mutational status of MYD88/CD79B did not lead to any difference in PFS and OS. We obtained the Tumor Mutational Burden (TMB) information from 11 patients. The median TMB was 15.96 (range: 3.82-28.11) muts/Mb. Kaplan-Meier analysis demonstrated that PFS was significantly longer in patients with higher TMB (≥15.96 muts/Mb) after zanubrutinib-based treatment(P=0.005). Grade ≥3 and serious treatment-emergent AEs (TEAEs) were not found. The most commonly TEAEs were hematologic toxicity (8/23,34.8%) and skin rash (5/23,21.7%). Conclusions: Our study demonstrates that zanubrutinib-based therapy is effective and safe for the treatment of R/R PCNSL. We advocate for the prolonged administration of zanubrutinib to maintain treatment response. Patients with higher TMB derive greater benefits from zanubrutinib-based regimens.