Capecitabine, Irinotecan Hydrochloride, Cetuximab, and Radiation Therapy in Treating Patients Undergoing Surgery for Locally Advanced Rectal Cancer

DISEASE CHARACTERISTICS: * Histologically confirmed adenocarcinoma of the rectum * MRI-defined locally advanced disease, as defined by 1 of the following: * Mesorectal fascia involvement * Mesorectal fascia threatened (tumor ≤ 1 mm from mesorectal fascia) * Any T3 tumor \< 5 cm from anal verge * No evidence of metastatic disease PATIENT CHARACTERISTICS: * ECOG or WHO performance status 0-1 * ANC ≥ 1.5 x 10\^9/L * Platelet count ≥ 100 x 10\^9/L * Serum bilirubin \< 1.25 times upper limit of normal (ULN) * Serum transaminase(s) \< 3 times ULN * Serum alkaline phosphatase \< 5 times ULN * Estimated glomerular filtration rate \> 50 mL/min * Not pregnant or nursing * Fertile patients must use effective contraception * Fit to receive all study treatments * Able to comply with oral medication * No comorbidity or coagulation problem that would deem the patient unsuitable for surgery * No pre-existing condition that would preclude radiotherapy (e.g., fistulas, severe ulcerative colitis \[particularly patients currently taking sulfasalazine\], Crohn's disease, prior adhesions) * No current or impending rectal obstruction (unless a defunctioning stoma is present) or metallic colonic rectal stent in situ * No significant small bowel delineated within the radiotherapy fields * No pelvic sepsis * No gastrointestinal disorder that would interfere with oral therapy or oral bioavailability * No uncontrolled cardiac, respiratory, or other disease that would preclude study therapy or informed consent * No serious medical or psychiatric disorder that would preclude study therapy or informed consent * No known dihydropyrimidine dehydrogenase deficiency PRIOR CONCURRENT THERAPY: * No prior chemotherapy * No prior radiotherapy to the pelvis * No concurrent participation in other studies, except genetic studies (e.g., NSCCG-National Study of Colorectal Cancer Genetics) * No concurrent St. John wort * No other concurrent cytotoxic treatment or radiotherapy