The prognosis of pancreatic cancer is extremely poor. NCCN guidelines recommend FOLFIRINOX or modified-FOLFIRINOX as the first-line chemotherapeutic regimen. Studies have shown that immunotherapy with Anti-PD-1 antibody can effectively increase the response rate and prolong patient survival in a number of cancer diseases. Here investigators intend to compare the therapeutic effects of modified-FOLFIRINOX alone and the combination of modified-FOLFIRINOX and Anti-PD-1 antibody in patients with metastatic pancreatic cancer.

Metastatic pancreatic cancer patients will be enrolled in this trial. Investigators will assign patients to the treatment after randomization. The primary endpoint is overall survival. Response rate, progression-free survival, drugs related side effects and other endpoints events will be recorded and analyzed, to assess the combination treatment with modified-FOLFIRINOX and Anti-PD-1 antibody could or couldn't benefit the patients with metastatic pancreatic cancer.

Inclusion Criteria:

• •Pathologically (histologically or cytologically) confirmed pancreatic ductal adenocarcinoma (PDAC).

  • Recurrent disease or metastatic disease (such as liver, peritoneum, lung) evaluated by abdominal contrast-enhanced CT, MRI, and chest CT. PET/CT or other imaging examinations would be used if necessary.
  • Never receive any systematic treatment or Progression after fisrt line Gemcitabine base chemotherapy
  • ECOG score 0 or 1.
  • Serum creatinine level is normal, and serum total bilirubin level is less than 1.5 x ULN.
  • ALT and AST are less than 2 x ULN.
  • Signed informed consent.

Exclusion Criteria:

• •History of participation of other clinical trails within 4 weeks

  • History of autoimmune disease or other condition receiving glucocorticoid treatment
  • History of receiving chemotherapy within 2 weeks
  • History of radiotherapy and molecular target therapy within 2 weeks
  • History if active tuberculosis
  • History of malignance treatment in the past, excluding basal and cutaneous squamous cell carcinoma, cervical carcinoma in situ, papillary thyroid carcinoma
  • Major cardiovascular diseases (including myocardial infarction, unstable angina, congestive heart failure, severe uncontrolled arrhythmia) during the past six months of enrollment.
  • Hematological precancerous diseases, such as myelodysplastic syndromes.
  • Evidence of clinical-related or previous interstitial lung disease, such as noninfectious pneumonia or pulmonary fibrosis, or baseline chest CT scan or chest X-ray findings
  • Previous or physical findings of central nervous system disease, except for adequately treated (e.g. primary brain tumors, uncontrolled seizures or strokes with standard medications)
  • Preexisting neuropathy > 1 (NCI CTCAE).
  • Immune deficiency syndrome, such as active tuberculosis and HIV infection.
  • Allograft requires immunosuppressive therapy or other major immunosuppressive therapies.
  • Severe serious wounds, ulcers or fractures.
  • Clinical evaluation is unacceptable