Capecitabine, Oxaliplatin, and Radiation Therapy in Treating Patients Who Are Undergoing Surgery for Stage I Rectal Cancer

Exclusion Criteria

• •Patients with the following conditions are NOT allowed on study:
• •* Metastatic disease or other primaries (patient must have had chest X-ray/computed tomography \[CT\] and abdominal \& pelvic CT/MRI with IV contrast, as well as a colonoscopy)
• •* Previously documented history of familial adenomatous polyposis
• •* Previously documented history of hereditary non-polyposis colorectal cancer diagnosed clinically (Amsterdam II criteria) or by genetic testing
• •* History of inflammatory bowel disease
• •* History of prior radiation treatments to pelvis
• •* Clinically significant peripheral sensory or motor neuropathy (defined as symptomatic weakness, paresthesia or sensory alteration described to be interfering with function, interfering with activities of daily living, disabling or life-threatening)
• •* History of any clinically significant cardiac disease (i.e., class 3-4 congestive heart failure, symptomatic coronary artery disease, uncontrolled arrhythmia, and/or myocardial infarction within the last 6 months)
• •* History of uncontrolled seizures or clinically significant central nervous system disorders
• •* History of psychiatric conditions or diminished mental capacity that could compromise the giving of informed consent, or interfere with study compliance
• •* History of allergy and/or hypersensitivity to capecitabine and/or oxaliplatin
• •* History of difficulty or inability to take or absorb oral medications
• •White blood cells (WBC) \>= 3000/mm\^3
• •Absolute neutrophil count (ANC) \> 1,500/mm\^3
• •Hemoglobin \> 9.5 mg/dl
• •Platelet count \>= 100,000/mm\^3
• •Total bilirubin =\< 3 mg/dl
• •Aspartate aminotransferase (AST) (serum glutamic oxaloacetic transaminase \[SGOT\]) and alanine aminotransferase (ALT) (serum glutamate pyruvate transaminase \[SGPT\]) =\< 2.0 times institutional upper limit of normal (ULN)
• •Alkaline phosphatase =\< 2.0 times ULN
• •Creatinine clearance (CLcr) \>= 50 ml/min by Cockroft-Gault equation
• •Patients who have experienced a prior malignancy must have received potentially curative therapy for that malignancy, and must be cancer-free for at least five years from the date of initial diagnosis (exceptions: patients treated for non-melanoma skin carcinoma, or in-situ carcinomas)
• •Patients of reproductive potential must agree to use an effective method of birth control when undergoing treatments with known or possible mutagenic or teratogenic effects; all female participants of childbearing potential must have a negative urine or serum pregnancy test within two weeks prior to study registration