DISEASE CHARACTERISTICS: Histologically proven locally recurrent prostate cancer that has failed conventional therapy (i.e., external beam radiotherapy, radioactive seed implants, and hormonal therapy) Must be confirmed clinically with elevated PSA and/or ultrasound Prostates between 2-5 cm in diameter (i.e., volumes of 4-65 cm3) preferred Prostates greater than 5 cm allowed, but 2 needles required for good distribution of study drug No clinical/radiographic evidence of metastatic disease No history of injury to urethra, bladder, or rectum