Capecitabine, Vorinostat, and Radiation Therapy in Treating Patients With Nonmetastatic Pancreatic Cancer

Inclusion Criteria: * Patient must have histologically confirmed pancreatic or periampullary cancer. * Patient must be \> 18 years of age. * Patient may be resectable, borderline resectable, or unresectable but locally advanced as determined by radiographic examination and consultation with a surgical oncologist. * Patient must have Eastern Cooperative Oncology Group (ECOG) performance score of 0-2. * Female patients of childbearing potential must be willing to use birth control. The 2 birth control methods can be either 2 barrier methods or a barrier method plus a hormonal method to prevent pregnancy, used throughout the study starting with visit 1. The following are considered adequate barrier methods of contraception: diaphragm, condom (by the partner) or sponge. Other methods of contraception such as copper intrauterine device or spermicide may be used. Appropriate hormonal contraceptives will include any registered and marketed contraceptive agent that contains an estrogen and/or a progestational agent (including oral, subcutaneous, intrauterine, or intramuscular agents).Female patient of childbearing potential has a negative serum pregnancy test β-hCG within 7 days prior to receiving the first dose of vorinostat. * Male patients agree to use an adequate method of contraception for the duration of the study. * Patient has a life expectancy of at least 12 weeks * Patient must have adequate organ function as indicated by the following laboratory values: * Absolute neutrophil count (ANC) ≥1,500 /mcL * Platelets ≥100,000 / mcL Hemoglobin ≥ 9 g/dL * Coagulation * Prothrombin Time or INR ≤1.5x upper limit of normal (ULN) unless receiving therapeutic anticoagulation * Partial thromboplastin time (PTT) ≤1.2 times the ULN unless the patient is receiving therapeutic anticoagulation. * K levels - Normal limits * Mg levels - Normal limits * Calculated creatinine \*clearance ≥20 mL/min * Serum total bilirubin ≤ 1.5 X ULN * AST (SGOT) and ALT (SGPT) ≤ 2.5 X ULN * Alkaline Phosphatase ≤ 2.5 X ULN \* Creatinine clearance should be calculated per institutional standard. * Patient must be capable of understanding and complying with the study protocol and able to give informed consent. * Measurable disease is not an eligibility requirement. Exclusion Criteria: * Prior chemotherapy for pancreatic or periampullary cancer. * Prior radiation to any area within the planned radiation field. All patients with history of prior radiation to any area must be approved by PI. * Evidence of distant metastases on imaging. * History of hypersensitivity to fluoropyrimidines or HDACs.