Combination Chemotherapy and Intensity-Modulated Radiation Therapy in Treating Patients Undergoing Surgery for Locally Advanced Rectal Cancer

DISEASE CHARACTERISTICS:

* Pathologically confirmed diagnosis of adenocarcinoma of the rectum by biopsy technique that does not completely excise the lesion (e.g., fine needle aspiration, core needle biopsy)

  * Located up to 12 cm from the anal verge with no extension of malignant disease into the anal canal
  * Clinically determined to be stage T3 or T4,N0-N2, and M0 tumor as determined by the following assessments:

    * Colonoscopy and biopsy within 56 days prior to registration
    * History/physical examination (including medication history screen for contraindications) within 56 days prior to registration
    * Contrast-enhanced imaging of the abdomen and pelvis either by computed tomography(CT), MRI, or Positron-emission tomography(PET)-CT (whole body preferred) within 56 days prior to registration
    * Chest x-ray (or CT) of the chest within within 56 days prior to registration to exclude distant metastases (except for patients who have had whole body PET-CT)
    * Transrectal ultrasound (TRUS) within 56 days prior to registration required to establish tumor stage

      * TRUS not required if clinical exam, CT of the pelvis, and/or MRI demonstrates T4 lesion
* No synchronous primary colon carcinoma
* No evidence of distant metastases (M1)

PATIENT CHARACTERISTICS:

Inclusion criteria:

* Zubrod performance status 0-2
* Absolute neutrophil count (ANC) ≥ 1,800/mm³
* Platelet count ≥ 100,000/mm³
* Hemoglobin ≥ 8.0 g/dL (transfusion or other intervention to achieve hemoglobin ≥ 8.0 g/dL allowed)
* Aspartate aminotransferase (AST) \< 2.5 times upper limit of normal (ULN)
* Alkaline phosphatase \< 2.5 times ULN
* Bilirubin ≤ 1.5 times ULN
* Creatinine clearance \> 50 mL/min
* Not pregnant or nursing
* Negative pregnancy test
* Fertile patients must use effective contraception
* No prior invasive malignancy except nonmelanoma skin cancer unless disease free for a minimum of 3 years

Exclusion criteria:

* Severe, active comorbidity, defined as follows:

  * Unstable angina and/or congestive heart failure requiring hospitalization within the past 12 months
  * Transmural myocardial infarction within the past 6 months
  * Acute bacterial or fungal infection requiring intravenous antibiotics
  * Chronic obstructive pulmonary disease exacerbation or other respiratory illness requiring hospitalization or precluding study therapy within the past 30 days
  * Hepatic insufficiency resulting in clinical jaundice and/or coagulation defects
  * AIDS
  * Evidence of uncontrolled seizures, central nervous system disorders, or psychiatric disability judged by the investigator to be clinically significant, precluding informed consent, or interfering with compliance of oral drug intake
  * Known, existing uncontrolled coagulopathy, unless clinically stable on anticoagulation therapy for ≥ 2 weeks
  * Evidence of peripheral neuropathy ≥ grade 2
* Prior allergic reaction to oxaliplatin or capecitabine
* Lack of physical integrity of the gastrointestinal tract (i.e., severe Crohn disease that results in malabsorption; significant bowel resection that would make one concerned about the absorption of capecitabine) or malabsorption syndrome that would preclude feasibility of oral chemotherapy (i.e., capecitabine)
* Prior systemic chemotherapy for colorectal cancer (prior chemotherapy allowed provided it was for a cancer other than colorectal cancer)
* Prior radiotherapy to the region of the study cancer that would result in overlap of radiotherapy fields
* Major surgery within 28 days of study enrollment(other than diverting colostomy without tumor resection)
* Participation in any investigational drug study within 28 days of study enrollment.
* Concurrent cimetidine, amifostine, and/or depot Sandostatin