Inclusion Criteria:  Age > 18 years old, male or female; Locally advanced or metastatic pancreatic ductal adenocarcinoma confirmed by histopathology / cytology of the primary and / or metastatic lesions and not suitable for surgical resection, and don't receive chemotherapy; According to the evaluation criteria of solid tumor efficacy(RECIST 1.1), there should be at least one measurable lesion (non nodular lesion with the longest diameter of 210 mm, or nodular lesion with the shortest diameter of more than 15 mm); Patients voluntarily participate in this study, sign informed consent, have good compliance, and cooperate with follow-up.  Exclusion Criteria:  If any of the following criteria is met, the patient should be excluded:  Pancreatic ductal adenocarcinoma is diagnosed without histopathology / cytology; The target lesion has received local non-drug therapy (including radiotherapy, physical and / or chemical ablation, etc.), and there is no imaging progression; If the central nervous system metastasis is known, MRI should be performed to exclude it.