DISEASE CHARACTERISTICS:

* Histologically confirmed adenocarcinoma of the rectum

* T1 or T2 by physical and endoscopic exams
* No T3 lesions by clinical or radiological exam
* Villous adenomas or in situ carcinoma allowed without histologicalconfirmation if clinical appearance of cancer
* No multi-focal disease within the rectum at time of initial diagnosis
* No non-adenocarcinomatous rectal cancer or anal cancer
* Less than 4 cm at greatest diameter
* Less than 40% of rectal wall circumference involved
* Proximal margin no greater than 8 cm from dentate line
* No tumor fixation to the perirectal tissues regardless of size
* No malignant regional lymph node or distant metastases by clinical exam orradiographical imaging

* No palpable perirectal lymph nodes or nodes larger than 1 cm
* No evidence of malignant perirectal lymph nodes by endorectal ultrasound orendorectal MRI

PATIENT CHARACTERISTICS:

Age:

* 18 and over

Performance status:

* CTC 0-2

Life expectancy:

* Not specified

Hematopoietic:

* WBC at least 4,000/mm\^3
* Platelet count at least 100,000/mm\^3

Hepatic:

* Bilirubin less than 1.5 times normal

Renal:

* Creatinine less than 1.8 mg/dL

Other:

* Not pregnant or nursing
* Negative pregnancy test
* Fertile patients must use effective contraception
* No other prior or concurrent malignancy within the past 5 years except inactive nonmelanomatous skin cancer or carcinoma in situ of the cervix

PRIOR CONCURRENT THERAPY:

Biologic therapy:

* Not specified

Chemotherapy:

* No prior chemotherapy

Endocrine therapy:

* Not specified

Radiotherapy:

* No prior radiotherapy

Surgery:

* No prior surgery for rectal cancer including prior attempts at transanal or transcoccygeal surgical excision with unclear or positive margins
* Prior incision or operative biopsy or colonoscopic removal allowed