Adenocarcinoma/radiotherapy; Antimetabolites, Antineoplastic/therapeutic use; Chemotherapy, Adjuvant; Deoxycytidine/therapeutic use; Pancreatic Neoplasms/radiotherapy; Radiotherapy, High-Energy; Adenocarcinoma/drug therapy; Adenocarcinoma/mortality; Adenocarcinoma/pathology; Adenocarcinoma/surgery; Adult; Antimetabolites, Antineoplastic/administration & dosage; Antimetabolites, Antineoplastic/adverse effects; Bone Marrow Diseases/etiology; Chemotherapy, Adjuvant/adverse effects; Combined Modality Therapy; Deoxycytidine/administration & dosage; Deoxycytidine/adverse effects; Deoxycytidine/analogs & derivatives; Disease-Free Survival; Drug Administration Schedule; Fatigue/etiology; Female; Follow-Up Studies; Gastrointestinal Hemorrhage/etiology; Humans; Male; Middle Aged; Nausea/etiology; Pancreatectomy; Pancreatic Neoplasms/drug therapy; Pancreatic Neoplasms/mortality; Pancreatic Neoplasms/pathology; Pancreatic Neoplasms/surgery; Radiotherapy Dosage; Radiotherapy Planning, Computer-Assisted; Radiotherapy, High-Energy/adverse effects; Remission Induction; Survival Analysis; Treatment Outcome; Gemcitabine