Gemcitabine and Celecoxib Combination Therapy in Treating Patients With R0 Resection Pancreatic Cancer

Inclusion Criteria: 1. 18 years old and above. 2. Surgery for R0 resection. 3. The gemcitabine chemotherapy regimen was not previously used for the treatment of other malignancies. 4. Eastern Cooperative Oncology Group score 0-2 points. 5. Blood routine: The neutrophil count is at least 1.5\*10\^9/ml, and the platelet count is at least 100\*10\^9/ml.Hemoglobin is at least 80g/L. 6. Liver function: bilirubin does not exceed 1.5 times the upper limit of normal; alanine aminotransferase and aspartate aminotransferase does not exceed the upper limit of normal 3 times; kidney function: creatinine ≤ 1.2 mg/dL. Exclusion Criteria: 1. Endocrine carcinoma, acinar pancreatic carcinoma, or cystadenocarcinoma (cystadenocarcinoma). 2. Surgery for pancreatic cancer fails to reach the R0 resection criteria. 3. Pancreatic cancer received radiotherapy before surgery. 4. Malignant brain metastases. 5. There are other serious cancer history. 6. Active infection, severe diarrhea. 7. Others: Those who are allergic to celecoxib; or who are intolerant to celecoxib, require continuous aspirin or Non-steroidal anti-inflammatory drugs; similar chemical or biological components and sulfa drugs that constitute the study drug History of allergies; allergies, asthma, and rubella after taking aspirin or non-steroidal anti-inflammatory drugs; pregnancy or breastfeeding; active gastrointestinal ulcer/hemorrhage/perforation; Severe mental illness; severe heart failure; past serious cardiovascular thrombotic adverse events, severe hypertensive patients.