Transrectal ultrasonography for prostatic cancer: its value in staging and monitoring the response to radiotherapy and chemotherapy.

Current methods to evaluate the size and local extent of prostatic cancer are imprecise. Quantitative assessments of changes after therapy are unreliable. We have used transrectal ultrasonography in 50 patients with clinically localized prostatic cancer to determine the value of this imaging technique in staging the local tumor and in monitoring the response of the tumor to therapy. Transverse images of the prostate were obtained at 5 mm. intervals, and were used to determine the size and shape of the prostate, irregularity or discontinuity of the capsule, extracapsular extension of tumor and invasion into the seminal vesicles. Ultrasonography proved highly accurate in staging. Among 18 previously untreated patients whose tumor appeared to be confined to the prostate by rectal examination 8 (44 per cent) had extension beyond the prostate by ultrasonography, which was confirmed by operative findings. Serial ultrasonograms were performed before and after definitive radiotherapy in 7 patients and chemotherapy in 6 patients. In response to therapy the prostate decreased in size and resumed a more normal, symmetrical shape, the capsule reformed and thickened, the degree of extracapsular extension diminished and the seminal vesicles became normal. Maximal reduction in the size of the prostate usually occurred by 9 months after radiotherapy and by 3 months after chemotherapy. In patients with prostatic cancer transrectal ultrasonography is highly accurate in staging and offers an objective monitor of the response to therapy.