Transrectal ultrasound in monitoring response to treatment of prostate disease.

Transrectal ultrasound provides a safe method for repeated assessments of the prostate gland in the follow-up of prostatic cancer. Changes in the echo pattern of the gland may be observed following treatment, but these may be difficult to interpret. The capsule may be restored; the tumor may appear smaller, and in some cases, ultrasound identification of the tumor may become impossible. The total gland volume decreases with chemotherapy and hormonal manipulation (subcapsular orchidectomy or drug-induced). The volume generally decreases after radiotherapy but may show a transient increase if there is some associated radiation proctitis. The rate of decrease of total prostatic volume has not been established as a reliable indicator of the subsequent prognosis. Future studies should assess whether sequential measurements of the tumor volume rather than the total prostatic volume may be a more useful guide to prognosis.