The Efficacy and Safety of Pola-ZR2 Versus ZR2 in the Treatment of Old Patients With de Novo Diffuse Large B-cell Lymphoma

Inclusion Criteria: Patients must satisfy all of the following criteria to be enrolled in the study: * Histologically-confirmed diffuse large B-cell lymphoma (without central nervous system involvement) * Aged ≥ 80 years old or aged 70-79 with comprehensive geriatric assessment stratified as unfit or frail * International prognostic index score 2 to 5 * At least 1 measurable site of disease (defined as lymph nodes with the long diameters longer than 1.5cm, or extra-nodal sites with the long diameters longer than 1.0cm; meanwhile, any lesion site with at least 2 measurable vertical diameters) * Able to swallow capsules * Life expectancy of at least 3 months determined by researchers * The patient or his or her legal representative must provide written informed consent prior to any special examination or procedure for the research. * Anti-lymphoma drugs have not been used before (except glucocorticoids) Exclusion Criteria: Presence of any of the following criteria will exclude a patient from enrollment: * Uncontrolled blood clotting disorders, connective tissue diseases, serious infectious diseases and other diseases * Laboratory measures meet the following criteria at screening (unless caused by lymphoma): Neutrophils\<1.5×10\^9/L Platelets\<80×10\^9/L ALT or AST is 2 times higher than the upper limits of normal (ULN), serum bilirubin are 1.5 times higher than the ULN. Creatinine is 1.5 times higher than the ULN or eGFR is lower than 40ml/min/1.73m\^2 (according to Cockcroft-Gault Equation or MDRD Equation). * uncontrollable or significant cardiovascular diseases, including but not limited to: Left ventricular ejection fraction\<50% Cardiomyopathy, such as dilated cardiomyopathy, hypertrophic cardiomyopathy, restrictive cardiomyopathy QTc prolongation with clinical significance, QTc interval\>470ms (females) or 480ms (males), type 2 second-degree atrioventricular block or third-degree atrioventricular block * Patients with HbsAg positive are required to have HBV DNA\<1.0×10\^3 IU/ml before entering the group. In addition, if the patient is HBsAg negative but HBcAb positive (regardless of HBsAb status), HBV DNA test is also required, and HBV DNA\<1.0×10\^3 IU/ml is required before entering the group * Patients with psychiatric disorders or patients who are known or suspected to be unable to fully comply with the study protocol * HIV-infected patients * History of stroke or intracranial hemorrhage within 6 months prior to start of therapy * Other medical conditions determined by the researchers that may affect the study