Inclusion Criteria:

- Histologically proven previously untreated adenocarcinoma of the rectum thatbegins
within 12 cm of the anal verge by sigmoidoscopy and/or colonoscopy

- Locally advanced disease defined as any of the following:

- Fixed or immovable tumor on physical exam

- T4 disease with invasion of adjacent structures (e.g., pelvic sidewall,
sacral pelvis, bladder, or prostate) by CT scan, rectal ultrasound, or MRI

- T3 disease with invasion through the wall of the muscularis propria by
transrectal ultrasound, CT scan, or MRI

- No distant metastatic disease

- Performance status - ECOG 0-2

- Granulocyte count at least 1,500/mm^3

- Platelet count at least 100,000/mm^3

- Bilirubin no greater than upper limit of normal (ULN)

- SGOT/SGPT no greater than 2.5 times ULN

- Creatinine no greater than 1.5 mg/dL

- Creatinine clearance at least 60 mL/min

- No active second malignancy except nonmelanomatous skin cancer or carcinoma in situ
of the cervix

- Patients are not considered to have an active second malignancy if they have
completed therapy and are at less than 30% risk of relapse

- No prior or concurrent evidence of neuropathy

- No history of allergy to platinum compounds or antiemetics

- Not pregnant or nursing

- Fertile patients must use effective contraception

- No prior fluorouracil or platinum-based therapy for any malignancy

- No other concurrent chemotherapy

- Hormonal therapy allowed only for non-disease related conditions (e.g., insulin for
diabetes) OR intermittently as an antiemetic (e.g., dexamethasone)

- No prior pelvic irradiation

- No concurrent antiretroviral therapy (HAART) for HIV positive patients