External-Beam Radiation Therapy, Capecitabine, and Sorafenib in Treating Patients With Locally Advanced Rectal Cancer

RATIONALE: Radiation therapy uses high-energy x-rays to kill tumor cells. Drugs used in chemotherapy, such as capecitabine, work in different ways to stop the growth of tumor cells, either by killing the cells or by stopping them from dividing. Sorafenib may stop the growth of tumor cells by blocking some of the enzymes needed for cell growth and by blocking blood flow to the tumor. Giving radiation therapy together with capecitabine and sorafenib before surgery may make the tumor smaller and reduce the amount of normal tissue that needs to be removed. PURPOSE: This phase I/II trial is studying the side effects and best dose of capecitabine when given together with sorafenib and external-beam radiation therapy and to see how well it works in treating patients with locally advanced rectal cancer.