PRIOR CONCURRENT THERAPY: Biologic therapy: At least 4 weeks since prior biologic therapy No concurrent experimental biologic therapy Chemotherapy: See Disease Characteristics Endocrine therapy: Not specified Radiotherapy: No prior radiotherapy compromising the delivery of radiation on this study No prior radiotherapy to areas within the planned field of treatment Surgery: At least 4 weeks since prior gastrointestinal surgery Other: At least 4 weeks since prior experimental drugs No other concurrent experimental drugs