OBJECTIVES: I. Determine the incidence, grade, and time course of acute grade 2 or higher gastrointestinal and genitourinary toxicities in patients with primary prostate adenocarcinoma receiving amifostine plus fractionated radiotherapy. II. Determine the incidence and nature of toxicity associated with amifostine in these patients. III. Assess tumor response to this treatment in these patients. IV. Assess impotency rates following radiotherapy in these patients.