In this prospective study, all the eligible patients will be given Pola-R2 regimen(polatuzumab vedotin 1.8 mg/kg ivgtt D1, rituximab375 mg/m2 ivgtt D1, lenalidomide 25mg po D1-14, one cycle every 21 days). An interim evaluation will be performed after 4 cycles, the patients who achieve CR or PR will receive another 4 cycles of Pola-R2.
The patients with stable disease (SD) or progressed disease (PD) will withdraw from the trial and receive salvage regimens.
