Transrectal sonography for serial evaluation of prostatic malignancy.

Serial changes in the prostatic bed as identified by transrectal sonography in 31 patients with prostatic carcinoma were correlated with systemic change in disease. Seventy-three sonograms were performed, allowing interval change to be evaluated in 42 instances. Sonography demonstrating regression correlated with clinical response in 89 percent (8/9) of studies and with disease progression in 91 percent (10/11). Stable disease was correctly evaluated by sonography in only 56 percent (10/18) of studies. Six of those 8 incorrectly identified as stable were in men with prostatic irradiation prior to inclusion in this study. If they are excluded, stability was accurately gauged in 83 percent (10/12). Stability of the prostate on serial sonography may not accurately reflect clinical status in men with prior prostatic irradiation. In 1 patient abscess was superimposed on and could not be differentiated from tumor. Nodules of increased, decreased, and mixed echogenicity showed the same response to treatment as the total prostate volume.