DISEASE CHARACTERISTICS:

• Histologically confirmed adenocarcinoma of the rectum

  • Stage II or III (T3-4, N0, M0 or any T, N1-3, M0)

• No distant metastases

  • No evidence of tumor outside of the pelvis, including liver metastases, peritoneal seeding, or metastatic inguinal lymphadenopathy
• Distal border of the tumor must be or have been at or below the peritoneal reflection, defined as within 12 cm of anal verge by protoscopic examination* NOTE: *Tumor with a portion confirmed to be below the peritoneal reflection at the time of surgery is allowed regardless of the distance by endoscopy
• Transmural penetration of tumor through the muscularis propria by CT scan, endorectal ultrasound, or MRI (group 1)
• Tumor must be defined prospectively by the surgeon as clinically resectable or not (group 1)

• Tumor may be clinically fixed or initially not completely resectable (clinical stage T4, N0-2, M0) based on the presence of at least 1 of the following criteria (group 1):

  • Tumor adherent to the pelvic sidewall or sacrum on rectal examination
  • Hydronephrosis on CT scan or intravenous pyelogram OR ureteric or bladder invasion by cystoscopy and cytology or biopsy OR invasion into prostate
  • Vaginal or uterine involvement

PATIENT CHARACTERISTICS:

Age

• 18 and over

Performance status

• ECOG 0-1

Life expectancy

• Not specified

Hematopoietic

• Absolute neutrophil count at least 1,500/mm^3
• Platelet count at least 100,000/mm^3

Hepatic

• Bilirubin no greater than 1.5 times upper limit of normal (ULN)
• AST no greater than 3 times ULN

Renal

• Creatinine no greater than 1.5 times ULN

Other

• Not pregnant or nursing
• Negative pregnancy test
• Fertile patients must use effective contraception
• No other prior or concurrent malignancy except nonmelanoma skin cancer, carcinoma in situ of the cervix, or other treated non-pelvic cancer from which the patient has been disease-free for more than 5 years
• No active inflammatory bowel disease
• No other serious medical illness that would preclude study treatment

PRIOR CONCURRENT THERAPY:

Biologic therapy

• Not specified

Chemotherapy

• No prior chemotherapy

Endocrine therapy

• Not specified

Radiotherapy

• No prior radiotherapy to the pelvis
• No concurrent intraoperative radiotherapy and/or brachytherapy

Surgery

• See Disease Characteristics