Paricalcitol, Fluorouracil, and Radiation Therapy in Treating Patients With Rectal Cancer That Can Be Removed in Surgery

This randomized pilot clinical trial studies the side effects of giving paricalcitol together with fluorouracil and radiation therapy in treating patients with rectal cancer that can be removed in surgery. Paricalcitol may help rectal cancer cells become more like normal cells, and to grow and spread more slowly. Drugs used in chemotherapy, such as fluorouracil, work in different ways to stop the growth of tumor cells, either by killing the cells or by stopping them from dividing. Radiation therapy uses high energy x rays to kill tumor cells. It not yet known if chemotherapy and radiation therapy are more effective with or without paricalcitol in treating rectal cancer