Octreotide in Preventing or Reducing Diarrhea in Patients Receiving Chemoradiotherapy for Anal or Rectal Cancer

DISEASE CHARACTERISTICS: * Histologically confirmed primary anal or rectal cancer * No metastasis beyond the pelvic regional nodes * Must be scheduled to receive chemoradiotherapy PATIENT CHARACTERISTICS: Age * 18 and over Performance status * Not specified Life expectancy * Not specified Hematopoietic * Not specified Hepatic * Liver function tests \< 3 times upper limit of normal * No prior hepatic disease Renal * Not specified Gastrointestinal * No prior chronic or acute regional enteritis * No malabsorption syndrome * No prior inflammatory bowel disease that may exacerbate the radiotherapy toxicity * No grade 2 or greater uncontrollable diarrhea at baseline * No prior cholecystitis or gallstones, unless a cholecystectomy has been performed * No prior incontinence of stool Other * Not pregnant or nursing * Negative pregnancy test * Fertile patients must use effective contraception * HIV negative * No uncontrolled diabetes (e.g., fasting glucose \> 250 mg/dL) * No prior allergy or hypersensitivity to study drug or other related drug or compound * No other medical condition or mental impairment that would preclude study treatment and compliance PRIOR CONCURRENT THERAPY: Biologic therapy * Not specified Chemotherapy * See Disease Characteristics * Prior chemotherapy allowed Endocrine therapy * At least 6 months since prior administration of any of the following: * Glucocorticoid therapy * Insulin sensitizers (e.g., metformin, pioglitazone, or r…