Zanubrutinib Plus Lenalidomide for Frail Elderly Patients With Newly Diagnosed PCNSL

Inclusion Criteria 1. Age ≥ 70 years. 2. patients classified as "Frail"according to the simplified Geriatric Assessment (sGA): --ADL ≤ 4 residual functions, or * IADL ≤ 5 residual functions, or * CIRS: ≥ 1 comorbidity of grade 3-4 or \> 8 comorbidities of grade 2, or * Age ≥ 80 years with "UNFIT" profile "UNFIT" profile: ADL = 5 residual functions or IADL = 6-7 residual functions, or CIRS: 0 comorbidity of grade 3-4 and 5-8 comorbidities of grade 2. 3. Voluntary provision of written informed consent. 4. Eastern Cooperative Oncology Group (ECOG) performance status of 0-3. 5. Considered able to safely undergo lumbar puncture. 6. Life expectancy of ≥ 3 months, as judged by the investigator. 7. Histologically confirmed diffuse large B-cell lymphoma (DLBCL) confined to the central nervous system (CNS). 8. Hematologic function: absolute neutrophil count ≥ 1.5 x 10\^9/L, hemoglobin ≥ 90 g/L, and platelet count ≥ 80 x 10\^9/L. 9. Hepatic function: serum total bilirubin ≤ 1.5 x the upper limit of normal (ULN), and serum alanine aminotransferase and aspartate aminotransferase ≤ 2.5 x ULN. 10. Renal function: creatinine clearance ≥ 30 mL/min, as estimated using the Cockcroft-Gault formula, or serum creatinine ≤ 1.5 x ULN. 11. Coagulation function: international normalized ratio (INR) ≤ 1.5 and activated partial thromboplastin time (aPTT) ≤ 1.5 x ULN. 12. Female participants of childbearing potential must have a negative pregnancy test within 7 days before the first dose and agree not to donate oocytes for reproductive purposes throughout the treatment and follow-up periods. Their male sexual partners must use condoms during sexual intercourse. 13. Male participants with female partners of childbearing potential must use condoms during sexual intercourse throughout the study and refrain from donating or cryopreserving sperm during this period. 14. Participants with stable and adequately controlled comorbidities may be enrolled, including those with hypertension (blood pressure ≤ 160/100 mmHg), type 2 diabetes mellitus (HbA1c ≤ 8%), or mild coronary artery disease without myocardial infarction within the preceding 6 months. Exclusion Criteria 1. Any disease or condition that may impair drug absorption (e.g., active inflammatory gastrointestinal disease, active gastric ulcer, chronic diarrhea, dysphagia, prior gastrectomy, gastroparesis, or short bowel syndrome). 2. Known hypersensitivity to zanubrutinib, lenalidomide, or any excipient contained in either drug. 3. Active bleeding within 1 month before treatment; a need for therapeutic anticoagulation during the study (e.g., warfarin or other vitamin K antagonists); or any condition associated with an increased risk of bleeding or coagulopathy (e.g., high-risk esophageal varices or active ulcer disease). 4. High risk of thrombosis. 5. Concurrent participation in another interventional clinical study (participation in noninterventional observational studies is permitted). 6. Major surgery within 4 weeks before treatment or an incompletely healed surgical incision. 7. Treatment with systemic corticosteroids within 4 weeks before treatment. 8. Another active malignancy or a history of another malignancy within 5 years before the initiation of study treatment, except for malignancies adequately treated with curative intent, such as basal cell or squamous cell carcinoma of the skin, cervical carcinoma in situ, or ductal carcinoma in situ of the breast. 9. Receipt of any vaccine, including but not limited to a vaccine against COVID-19, influenza, pneumonia, herpes zoster, or hepatitis B, within 4 weeks before the first dose. 10. Requirement for treatment with a moderate or strong CYP3A4/5 inhibitor or inducer within 2 weeks before the first dose or during the study; 11. Stroke or intracranial hemorrhage within 6 months before the first dose. 12. Known liver disease, including but not limited to alcoholic liver disease, cirrhosis, active hepatitis B virus (HBV) infection (detectable HBV DNA), active hepatitis C virus (HCV) infection (detectable HCV RNA), or other active hepatitis. Participants with HBV DNA below the limit of detection or cured HCV infection are not excluded. Participants with HBV or HCV infection may be enrolled after antiviral therapy, provided that HBV DNA is below the limit of detection or HCV RNA is undetectable, as applicable. 13. Active syphilis. 14. Human immunodeficiency virus (HIV) infection 15. Epstein-Barr virus (EBV) infection 16. An active infection requiring systemic treatment or unexplained fever with a body temperature ≥ 38.5℃ within 1 week before treatment; 17. Any of the following cardiac or cardiovascular criteria: （1）A heart rate-corrected QT interval calculated using Fridericia's formula (QTcF) \> 470 ms in females or \> 450 ms in males, or other risk factors for QT-interval prolongation or arrhythmic events (e.g., hypokalemia or a personal or family history of long QT syndrome); （2）A clinically significant arrhythmia or other cardiovascular disease requiring clinical intervention, including but not limited to acute myocardial infarction, unstable angina, or coronary artery bypass grafting within 6 months before treatment; congestive heart failure of New York Heart Association (NYHA) class II or higher; left ventricular ejection fraction (LVEF) \< 50%; hypertension not controlled with medication (systolic blood pressure \> 160 mmHg or diastolic blood pressure \> 100 mmHg); atrial fibrillation of European Heart Rhythm Association (EHRA) class ≥ 2b; or primary cardiomyopathy. 18\. Prior organ transplantation or allogeneic stem cell transplantation. 19\. Prior or current pulmonary fibrosis, interstitial pneumonia, pneumoconiosis, or radiation pneumonitis considered by the investigator to render the patient unsuitable for the study. 20\. An autoimmune disease requiring systemic treatment within the previous 2 years. 21\. Incomplete clinical data (e.g., no pathology report or inability to undergo MRI or PET/CT assessment). 22\. Pregnant (positive pregnancy test before dosing) or breastfeeding. 23\. Any other disease, psychiatric disorder, metabolic abnormality, physical examination finding, or clinically significant laboratory abnormality that, in the investigator's judgment, may compromise the participant's adherence to the study requirements, expose the participant to an unacceptable risk, interfere with the interpretation of the study results, or otherwise render the participant unsuitable for treatment with the study drugs. 24\. Any other circumstance that, in the investigator's judgment, renders the patient unsuitable for participation in the study.