Different Patterns of Target Delineation in SBRT for Locally Advanced Pancreatic Cancer

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