A Clinical Study on the Efficacy and Safety of Methotrexate (MTX) or Thiotepa (for MTX Intolerance) or Temozolomide (TMZ) Combined With Orelabrutinib and Selinexor in Relapsed/Refractory Primary or Secondary Central Nervous System Lymphoma（SELINA）

Inclusion Criteria: * Patients must meet all of the following criteria to be enrolled in this study: * Fully understand this study and voluntarily sign the informed consent form; * Age: 14-80 years; * Life expectancy judged by the investigator to exceed 3 months; * B-cell origin central nervous system lymphoma (CNSL) confirmed by pathology or flow cytometry (histology or cytology); * Relapsed or refractory PCNSL or SCNSL: Must have received at least one prior systemic therapy for CNS lesions; number of relapses is not restricted; * Any non-hematological toxicity related to prior treatment should have recovered to Grade 1 or normal (according to NCI CTCAE version 5.0, except alopecia). * Bone marrow and organ function meeting the following criteria (no transfusion, no G-CSF use, no medication for correction within 14 days before screening): Bone marrow function: Absolute neutrophil count ≥1.0x10⁹/L, platelets ≥50x10⁹/L, hemoglobin ≥60g/L;Liver function: Serum total bilirubin ≤1.5xULN (≤3.0xULN if liver metastases present); AST and ALT ≤ 2.5xULN (≤5.0xULN if liver metastases present);Coagulation function: International Normalized Ratio (INR) and activated partial thromboplastin time ≤1.5xULN;Renal function: Serum creatinine ≤1.5xULN or estimated creatinine clearance ≥30 mL/min (Male: Cr (mL/min) = (140 - age) x weight (kg) / (72 x serum creatinine (mg/dL)); Female: Cr (mL/min) = (140 - age) x weight (kg) / (85 x serum creatinine (mg/dL))). * Female subjects of childbearing potential and male subjects with reproductive ability, who have no pregnancy plan with their partners during the study period and for 3 months after treatment interruption, must use one of the following effective contraceptive methods throughout the study and for 3 months after treatment interruption: abstinence, physical contraception (e.g., ligation, condoms, etc.), hormonal contraceptive drugs started at least 3 months before the first dose in the study. Male subjects are prohibited from sperm donation from the start of treatment until 3 months after treatment cessation. The patient or their legal guardian voluntarily signs the informed consent form. * Good compliance, willing to adhere to the visit schedule, dosing plan, laboratory tests, and other trial procedures. Exclusion Criteria: * Patients who meet any of the following criteria will not be allowed to enter this study: * Contraindication to any drug in the treatment regimen; * Subject has a history of active liver disease, including viral or other hepatitis or cirrhosis (Hepatitis B defined as HBV-DNA above the upper limit of normal; active Hepatitis C defined as seropositive for HCV antibody, but those with negative HCV-RNA can be enrolled); * Human Immunodeficiency Virus (HIV) infection; * Congestive heart failure (New York Heart Association Class \>2); history of acute myocardial infarction, unstable angina, stroke, or transient ischemic attack within the past six months; * Hereditary long QT syndrome or QTc \>480ms (Note: QTc interval must be calculated using Fridericia's formula, QTcF = QT/(RR)\^0.33); * Pregnant and lactating women, or those planning to become pregnant during the study period; * Clear history of neurological or psychiatric disorders, or history of psychotropic drug abuse or drug addiction; * Clinically significant active infection.