The purpose of this multi-center,single arm,phase Ⅱ clinical trail is to determine the safety and efficacy of Sintilimab with P-GemOx (pegaspargase, gemcitabine and oxaliplatin) regimen for newly diagnosed advanced extranodal natural killer/T-cell lymphoma, nasal type (ENKTL)

Inclusion Criteria:

• biopsy proved extranodal natural killer/T-cell lymphoma, nasal type;
• newly diagnosed stage III/IV patients;
• at least one evaluable lesion；
• ECOG PS 0-2;
• 18-75 years; without other malignancy;
• proper functioning of the major organs.

Exclusion Criteria:

• hemophagocytic syndrome or aggressive NK cell leukemia;
• involvement of central nervous system;
• previously received treatment of chemotherapy, radiotherapy, immunotherapy or biotherapy for lymphoma；