Chidamide + R-GemOx Regimen as Salvage Treatment for Transplant-ineligible Patients With Relapsed/Refractory DLBCL

Inclusion Criteria: * biopsy proved CD20+ DLBCL; * relapse or refractory DLBCL# * previously received systemic chemotherapy with anthracycline# * not eligible for autologous hematopoietic stem cell transplantation# * at least one evaluable lesion# * ECOG PS 0-1; * 18-75 years; without other malignancy; * proper functioning of the major organs. Exclusion Criteria: * double-hit lymphoma; * previously received treatment of HDAC inhibitor; * plan to receive autologous stem cell transplantation; * involvement of central nervous system; * previously received gemcitabine within the past 6 months; * patients who received treatment for hematologic toxicity caused by previous chemotherapy within 7 days before enrollment;