Zanubrutinib

This is a prospective, single-arm, phase II clinical study evaluating the efficacy and safety of Zanubrutinib (a BTK inhibitor) plus Lenalidomide (an immunomodulatory drug) in frail elderly patients with newly diagnosed primary central nervous system lymphoma (PCNSL). The study plans to enroll 33 patients who are aged ≥ 70 years and classified as frail, a population for whom standard first-line treatment regimens, high-dose methotrexate-based chemotherapy, may be "unfit". This study includes screening phase, induction phase, consolidation phase and maintenance phase. The screening period is defined as within 1 week prior to the first dose. During induction, participants will receive Zanubrutinib 160 mg orally twice daily continuously and Lenalidomide 25 mg orally once daily on days 1-21 of each 28-day cycle for three cycles. Participants who achieve a partial response (PR) or complete response (CR) after induction will receive three additional 28-day consolidation cycles of the same regimen. Participants who achieve a CR after consolidation will continue maintenance treatment with Zanubrutinib and Lenalidomide until disease progression. Treatment response will be assessed throughout the study using the International Primary CNS Lymphoma Collaborative Group (IPCG) criteria and assessed every 3 months. The primary endpoint is the complete response rate (CRR) at the end of induction therapy. Secondary endpoints include overall response rate (ORR) at the end of induction therapy, CRR and ORR at the end of consolidation therapy, One-year and two-year progression-free survival (PFS) rates, Duration of response (DOR), overall survival (OS), adverse event (AE) and serious adverse event (SAE). Exploratory liquid-biopsy analyses will be performed to evaluate treatment response and prognosis.