Eligible patients will have histologically confirmed rectal adenocarcinoma, AJCC Stage IIA IIIC or AJCC Stage IV appropriate for consideration of primary rectal tumor resection. Patients will undergo a forceps biopsy of the rectal mass as part of the diagnostic workup as well as undergo staging evaluation including an MRI with additional study sequences. Enrolled patients will receive a 14 day course of LY2157299 followed by a repeat biopsy and MRI with study sequences. In this trial the investigators plan to use the maximum tolerated dose of LY2157299 established in human clinical trials, 300mg delivered as 150mg P.O. BID. On day 15 patients will begin chemoradiation with either 5-FU (fluorouracil ) or capecitabine (Xeloda®). On day 29, patients will undergo another fourteen day course of LY2157299 concurrent with their ongoing chemoradiation.