The early symptoms of pancreatic cancer are not obvious, and the early diagnosis rate is low. For most patients with pancreatic cancer,palliative chemotherapy is the only choice .At present, The guidance of NCCN guidelines on the selection of chemotherapy regimens for patients with advanced pancreatic cancer is only based on the physical condition(the ECOG score), which is one of the important reasons for the poor efficacy of chemotherapy in patients with advanced pancreatic cancer.Therefore, it is urgent to group pancreatic cancer patients according to tumor molecular typing and heterogeneity of response to chemotherapy drugs accurately,so as to guide the personalized treatment of patients.

Based on the limitations of existing studies and the needs of clinical patients, the investigators chose two time points: after the diagnosis of pancreatic cancer (before the first-line chemotherapy), and after chemotherapy evaluation in this study, to obtain in situ samples of pancreatic cancer tissues by EUS-FNA.The samples are detected by dynamic multi-omics study before and after treatment(including genomics, transcriptomics, proteomics, metagenomics, etc.).Combined with the drug reaction and clinical outcome of patients, a comprehensive model is established to predict the clinical outcome of patients with PDAC and the choice of chemotherapy regimens, so as to screen the pancreatic cancer patients who are most likely to benefit from different chemotherapy regimens, and lay the foundation for the development of individual chemotherapy for advanced pancreatic cancer.

Inclusion Criteria:

1. Age > 18 years old, male or female;
2. 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;
3. 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);
4. 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:

1. Pancreatic ductal adenocarcinoma is diagnosed without histopathology / cytology;
2. The target lesion has received local non-drug therapy (including radiotherapy, physical and / or chemical ablation, etc.), and there is no imaging progression;
3. If the central nervous system metastasis is known, MRI should be performed to exclude it.

Patients with advanced pancreatic ductal adenocarcinoma