Chemoimmunotherapy and Radiation in Pancreatic Cancer

This study is for borderline resectable and advanced pancreatic cancer patients. Patients will receive chemotherapy with gemcitabine and immunotherapy with daily tadalafil during the first 21 days of treatment. On study day 22, patients will receive the first of three planned doses of radiation therapy and continue daily tadalafil. Patients are then evaluated to determine if they are candidates for pancreaticoduodenectomy. Patients who are not candidates will continue daily tadalafil and receive gemcitabine chemotherapy. Patients who have surgery will resume daily tadalafil and gemcitabine chemotherapy following recovery from surgery. Patients will receive up to four cycles of gemcitabine.