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

- Patient must have an Eastern Cooperative Oncology Group (ECOG)/Zubrod status of =< 2

   - Patient must have histologically confirmed invasive adenocarcinoma of the rectum;
   Note: patients with rectal tumors suspicious for invasion also are eligible

   - Distal border of the patient's tumor must be within 8 cm from the anal verge as
   measured on endoscopic exam

   - Patients with tumors fixed to adjacent structures on digital exam are NOT eligible

   - Patient must have an uT2uN0 tumor, as confirmed by endorectal ultrasound (ERUS) or
   endorectal coil magnetic resonance imaging (MRI) scan; patients with uT1, uT3, or uT4
   tumors are NOT eligible; greatest diameter of tumor cannot exceed 4 cm

   - Patients with positive perirectal nodes on ERUS examination are NOT eligible

   - Patients with histologic evidence of metastatic invasion of inguinal lymph nodes are
   NOT eligible

   - 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