Identification of residual cancer in the prostate following radiation therapy: role of transrectal ultrasound guided biopsy and prostate specific antigen.

Transrectal, ultrasound guided needle biopsies were performed in 27 men greater than 18 months (mean 5.2 years) after radiation therapy for prostate cancer. Of the patients 18 (67 per cent) originally had localized (stage A or B), 6 had stage C and 3 had stage D1 prostate cancer. In addition to biopsies directed at any hypoechoic regions of the prostate, multiple systematic biopsies were performed from the apex to the base bilaterally and the seminal vesicles also were biopsied regardless of appearance. Of 27 patients 25 (93 per cent) had post-irradiation biopsies positive for cancer, including 5 of 5 with prostate induration and 20 of 22 (91 per cent) with normal post-irradiation digital rectal examinations. Ultrasound findings per se were poorly correlated with pathological findings in the irradiated prostate. Directed biopsies of hypoechoic areas were positive for cancer in 67 per cent of the cases and isoechoic areas were positive for cancer in 65 per cent. Seminal vesicle biopsies were positive in 7 patients (26 per cent), including 4 with normal post-irradiation rectal examinations and 4 with normal ultrasound appearance. Of 12 patients 10 (83 per cent) with serum prostate specific antigen levels less than 10 ng. per ml. had positive biopsies, as did all 15 with levels greater than 10 ng. per ml.