The purpose of this study is to compare the efficacy and safety of a recurrence-pattern-based-volume versus conventional-volume stereotactic body radiation therapy for locally advanced pancreatic cancer, so as to determine whether the target delineation method based on recurrence pattern can obtain better survival benefits.

Inclusion Criteria:

• Cytologically or histologically verified pancreatic adenocarcinoma
• Imaging examinations confirmed locally advanced pancreatic cancer
• No previous radiotherapy, chemotherapy, immunotherapy or targeted therapy
• ECOG of 0 to1
• Age of 18 years or older
• Adequate bone marrow function, defined as: Absolute neutrophil count (ANC) ≥ 1.5×10^9 cells/L, leukocyte count≥ 3.5×10^9 cells/L, platelets ≥ 70×10^9 cells/L, hemoglobin ≥ 8.0 g/dl
• Adequate liver and renal, defined as: Albumin > 2.5 g/dL, total bilirubin < 3 mg/dL, creatinine < 2.0 mg/dL, AST<2.5 × ULN (Upper Limit of Normal) (0-64U/L), ALT<2.5 × ULN (0-64U/L)
• Adequate blood clotting function, defined as: international normalized ratio (INR) < 2 (0.9-1.1)
• Ability of the research subject or authorized legal representative to understand and the willingness to sign a written informed consent document

Exclusion Criteria:

• Previously receiving radiotherapy, chemotherapy, immunotherapy or targeted therapy
• Evidences of metastatic disease confirmed by chest CT or PET-CT
• ECOG ≥2
• Age <18 years
• Secondary malignancy
• Abnormal results of blood routine examinations and liver and kidney and coagulation tests
• Patients with active inflammatory bowel diseases or peptic ulcer
• Gastrointestinal bleeding or perforation within 6 months
• Uncontrolled infection requiring IV antibiotics, antivirals, or antifungals
• Medical history of symptomatic congestive heart failure: New York Heart Association Class III to IV
• Medical history of respiratory insufficiency
• Women who are pregnant or breastfeeding
• Participation in another clinical treatment trial
• Inability of the research subject or authorized legal representative to understand and the willingness to sign a written informed consent document

4 years