Sintilimab Plus R-CHOP as the First-line Treatment in Patients With Diffuse Large B-Cell Lymphoma.

Inclusion Criteria:

1. Diagnosed as diffuse large B-cell Lymphoma with positive CD20 results;
2. Age between 18 to 70 years old;
3. World health organization-Eastern Cooperative Oncology Group Performance Status (ECOG) 0-2;
4. No history of malignant tumors, having no tumor other than DLBCL at the time of enrollment;
5. Life expectancy no less than 6 months;
6. The patient or his/her attorney would be able to provide written consent for necessary examinations or procedures;
7. Ann Arbor stage I\~ IV
8. previously untreated advanced DLBCL.
9. At least one bi-dimensionally measurable lesion (greater than \[\>\] 1.5 centimeters in its largest dimension by CT scan or magnetic resonance imaging)
10. Availability of a representative tumor specimen and the corresponding pathology report for retrospective central confirmation of the diagnosis of DLBCL.
11. Agree to remain abstinent or use contraceptive measures.

Exclusion Criteria:

1. History of autologous stem cell transplantation,radiotherapy or chemotherapy.
2. History of other malignant tumors, except skin basal cell carcinoma and in situ cervical cancer;
3. With uncontrolled cardiovascular/ cerebrovascular disease, coagulation disorders, connective tissue disease, severe infectious diseases;
4. Lymphoma originated in the central nervous system;
5. Left ventricular ejection fraction ≦50％;
6. Abnormal lab results in enrollment:Neutrophil count: \<1.5\*10\^9/L；Platelet count \<75\*10\^9/L；AST or ALT \>2 times the upper limit of normal level，AKP and total bilirubin \>1.5 times the upper limit of normal level;serum creatinine \>1.5 times the upper limit of normal level;
7. Other uncontrolled medical conditions which the investigators think might influence the results of the trial;
8. Patients with mental illnesses or other diseases that might not comply with the trial plan;
9. Women during pregnancy or lactation;
10. HIV positive patients;
11. HbsAg (+) patients with HBV DNA(+), can be enrolled only when his/her HBV DNA turns negative; patients with HBsAg(-) HBcAb(+) can be enrolled only when his/her HBV DNA turns negative;