Latent residual tumor following external radiotherapy for prostate adenocarcinoma.

Fifty patients with adenocarcinoma of the prostate were treated by external supervoltage radiotherapy. Needle biopsies were obtained at timed intervals after completion of therapy. Six of 17 patients with stages A and B disease and 15 of 33 patients with stage C disease had positive biopsies. In patients biopsied more than 18 months after therapy 15 of 29 (52 per cent) had residual tumors. Of 17 patients biopsied 36 months or more after therapy 10 (59 per cent) had residual tumor. These results suggest that patients with residual tumor 18 months after therapy will not have resolution of the tumor at a future date and represent treatment failure.