To evaluate the efficacy and safety of the Pro-Pola （Pomalidomide, rituximab, orelabrutinib and polatuzumab vedotin) regimen in elderly patients (aged ≥70 years) with newly diagnosed diffuse large B-cell lymphoma (DLBCL).

The study will start with an initial 21-days of induction therapy with Pro regimen (Pomalidomide, rituximab and orelabrutinib)，following imaging examinations to evaluate response rates. Patients with a lesion reduction of ≥25% received Pro-pola(Pro regimen plus polatuzumab vedotin), in a 21-day cycle for 6 cycles.

Inclusion Criteria:

1. Age ≥70 years unfit or frail

2. There is at least one image-measurable lesion with a measurable lesion of at least 15 mm.

3. Histologically confirmed treatment-naive DLBCL.

4. Life expectancy is>3 months.

5. appropriate organ function: Cardiac function: Cardiac ejection fraction ≥50%; Liver function: alanine aminotransferase and aspartate aminotransferase ≤3 times the upper limit of normal; Renal function: Serum creatinine clearance ≥30mL/min; Lung function: SPO2 >90% without oxygen inhalation

6. Adequate bone marrow reserve is defined as:

   Hemoglobin ≥8g/dL, platelet count ≥75×10^9/L, Absolute neutrophil value ≥1.0×10^9/L, If accompanied by bone marrow invasion, platelet count ≥50×10^9/L, absolute neutrophil count ≥0.75×10^9/L.

7. Patients have the ability to understand and are willing to provide written informed consent.

8. Subjects with childbearing or childbearing potential must be willing to practice birth control from the date of registration in this study to the follow-up period of the study.

Exclusion Criteria:

1. Severe abnormal liver and kidney function (alanine aminotransferase, bilirubin, creatinine>3 times the upper limit of normal);
2. Presence of organic heart disease or severe arrhythmia leading to clinical symptoms or abnormal cardiac function (NYHA Functional Class Grade ≥2);
3. Uncontrolled active infection;
4. Co-existence of other tumors requiring treatment or intervention;
5. DLBCL involving central nervous system;
6. Current or expected need for systemic corticosteroid treatment;
7. Previous or current history of vascular embolism;
8. Other psychological conditions that prevent the patient from participating in the study or signing informed consent.
9. In the investigator's judgment, it is unlikely that the subject will complete all protocol-required study visits or procedures, including follow-up visits, or will not meet the requirements for participation in the study.