Two Stage Study of Combination of Chemotherapy, SHR-1210 and/or Decitabine for Relapsed/Refractory PMBCLs

This is a two stage, Phase I/II clinical trial for patients with relapsed or refractory primary mediastinal large B-cell lymphoma (rrPMBCL). In the first stage, the participants will receive GVD (Gemcitabine, Vinorelbine and Doxorubicine) chemotherapy and PD-1 antibody (SHR-1210) treatment. The safety and efficacy of combined regimen will be evaluated. If deemed safe and efficacious, the investigators will proceed to the second stage of the study. In the second stage, the participants will receive GVD chemotherapy and SHR-1210 treatment with low-dose Decitabine priming. The safety and feasibility of combined regimens will be evaluated in phase I study. The feasibility will be accessed.