This is a prospective, single-arm, phase II study, and the purpose of this study is to evaluate the efficacy and safety of Pola-R2 regimen in newly diagnosed elderly diffuse large B cell lymphoma classified into un-fit or frail group by comprehensive geriatric assessment(CGA).

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.

Inclusion Criteria:

• The patient volunteered to participate in the study and signed the Informed Consent
• Histopathologically confirmed DLBCL and treatment naive(corticosteroids alone is not considered as a line of treatment)
• Age≥ 70 years old, and was un-fit or frail according to comprehensive geriatric assessment
• Adequate organ function and adequate bone marrow reserve

Exclusion Criteria:

• Coexisting malignancy other than lymphoma
• Active HBV infection
• Any instability of systemic disease, including but not limited to active infection (except local infection), severe cardiac, liver, kidney, or metabolic disease need therapy