Decitabine and Anti-PD-1 in R/R DLBCL

Inclusion Criteria: 14-80 years old, male or female; Pathologically confirmed relapsed/refractory diffuse large B cell lymphoma with extranodal (central nervous system) involvement; Expected survival of more than 3 months; AST and ALT ≤ 3.0 ULN; TBIL and CCr ≤ 1.0 ULN; Inactive infection and severe mental illness ECOG score 0~2 According to the New York Heart Association (NYHA) cardiac function grading standards, the heart function grading should be grade I or Grade II; Cardiac ejection fraction >50% or not lower than the lower limit of the range of laboratory test values at the study center; No pathological abnormality was found in ECG; There was no clinically significant pericardial effusion or pleural effusion The serum pregnancy test of female subjects must be negative Signed informed consent Exclusion Criteria: Subjects with any autoimmune disease requiring long-term use of corticosteroids or immunosuppressive drugs or with a history of other tumors; Severe uncontrolled medical disease or active infection (including HIV+); Active gastrointestinal bleeding or 1 month history of gastrointestinal bleeding; Received allogeneic hematopoietic stem cell transplantation within 6 months or are participating in other clinical studies; Pregnant or nursing women; Subjects who must be forcibly detained for the treatment of mental or physical diseases (e.g. infectious diseases); The researcher thinks it is not suitable for this clinical study (such as poor compliance, drug abuse, etc.) The situation that the researcher judged was not suitable for inclusion