RATIONALE: Drugs used in chemotherapy work in different ways to stop the growth of tumor cells, either by killing the cells or by stopping them from dividing. Specialized radiation therapy that delivers a high dose of radiation directly to the tumor may kill more tumor cells and cause less damage to normal tissue. Giving these treatments before surgery may make the tumor smaller and reduce the amount of normal tissue that needs to be removed. Giving chemotherapy after surgery may kill any tumor cells that remain after surgery.

PURPOSE: This phase II trial is studying the side effects and how well giving combination chemotherapy together with intensity-modulated radiation therapy works in treating patients undergoing surgery for locally advanced rectal cancer.

OBJECTIVES:

Primary

• To determine whether the incidence of neoadjuvant acute gastrointestinal toxicity (grade ≥ 2) associated with neoadjuvant chemoradiotherapy is reduced by inverse-planned intensity-modulated radiotherapy (IMRT)-based radiation treatment when compared with conventionally delivered radiotherapy, as was utilized in the capecitabine and oxaliplatin arm of RTOG-0247 (NCT00081289).

Secondary

• To evaluate the feasibility of performing IMRT in a cooperative group setting for the treatment of rectal cancer.
• To estimate the incidence of all toxicity (hematologic and non-hematologic) associated with protocol treatment in the neoadjuvant period, the adjuvant period, and overall.
• To estimate the pathologic complete response rate following neoadjuvant IMRT-based chemoradiotherapy.
• To estimate the time to treatment failure and patterns of failure.
• To correlate pre- and post-treatment levels of serum cytokines with symptoms during and pathological outcomes following neoadjuvant chemoradiotherapy for rectal cancer.
• To evaluate the rate of abdominoperineal resections.

OUTLINE: This is a multicenter study.

• Chemoradiotherapy: Patients undergo inverse-planned intensity-modulated radiotherapy to the pelvis once daily, 5 days a week, for 5 weeks (total of 45 Gy) and a 3-dimensional conformal radiotherapy boost to gross disease once daily for 3 days (total of 45 Gy). Beginning on the first day of radiotherapy and continuing through completion of radiotherapy, patients receive oral capecitabine twice daily, 5 days a week, for 5 weeks and oxaliplatin IV over 2 hours on days 1, 8, 15, 22, 29.
• Surgery: Within 4-8 weeks after completion of chemoradiotherapy, patients undergo resection of the rectal tumor.
• Adjuvant chemotherapy: Beginning 4-8 weeks after surgery, patients with completely resected disease and negative surgical margins receive leucovorin calcium IV over 2 hours and oxaliplatin IV over 2 hours on day 1 and fluorouracil IV bolus on day 1 and fluorouracil IV infusion continuously over 46 hours beginning on day 1 . Treatment repeats every 14 days for up to 9 courses in the absence of disease progression or unacceptable toxicity.

Patients are followed every 3 months after the start of treatment for 2 years, every 6 months for years 3-5, and then annually thereafter.

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