Pre-operative 5-Fluorouracil (5-FU) and Sorafenib With External Radiation in Locally Advanced Rectal Cancer

The main purpose of this study is to find the maximum tolerable dose of sorafenib when administered along with another drug called 5-Fluorouracil (5-FU) and to find out more about whether these drugs, along with radiation, can help people with rectal cancer when given before surgery. 5-FU and radiation are both approved by the US Food and Drug Administration (FDA) for use in people with rectal cancer. The investigators will utilize a standard 3 + 3 phase I study design. In the phase I part of the study, the investigators will attempt dose escalation of sorafenib in combination with standard infusional 5-FU and external beam at standard doses. Clinical staging should be done by endorectal ultrasound (ERUS) and/or pelvic magnetic resonance imaging (MRI) for T and N stage; chest and abdomen computed tomography (CT) for staging of metastatic disease; undergo sigmoidoscopy and/or colonoscopy done by crude odds ratios (CORS); biopsy is taken for diagnosis and extra is sent for tissue bank. At the maximum tolerated dose (MTD) of sorafenib we will expand the cohort to 6 more patients to further evaluate toxicity profile and efficacy.