Prospective Clinical Study of ZPR Regimen in Relapsed/Refractory Diffuse Large B-cell Lymphoma

This is a prospective, single-arm, single-center clinical study. This clinical study aims to explore the efficacy and safety of the ZPR（Zanubrutinib, Polatuzumab vedotin and Rituximab）regimen in the treatment of patients with relapsed and refractory diffuse large B-cell lymphoma. * Primary objective: use ORR to evaluate the effectiveness of ZPR in treating R/R DLBCL patients * Secondary objective: Evaluate the safety of ZPR treatment for R/R DLBCL patients * The subjects received 6 cycles of ZPR regimen, one cycle every 21 days. Then Zanubrutinib alone will continue to be used until Zanubrutinib has been used for 1 year or the disease progresses or the adverse effects, death, withdrawal of informed consent or study termination. Zanubrutinib（Z）160 mg bid po Day 1-21; Polatuzumab vedotin（P）1.8 mg/kg ivgtt D1; Rituximab（R）375 mg/m2 ivgtt D1.