EFFECTS OF ENDOCRINE THERAPY ON THE PRIMARY LESION IN PATIENTS WITH PROSTATE CARCINOMA AS EVALUATED BY ENDORECTAL MAGNETIC-RESONANCE-IMAGING

BACKGROUND. Little effort has been made at the quantitative and qualit ative evaluation of patients with prostate carcinoma, including downsi zing and downstaging of the primary lesion, after conservative therapy . The current study was undertaken to investigate the qualitative and quantitative effects of endocrine therapy on the primary prostate carc inoma using magnetic resonance imaging (MRI). METHODS. The primary pro state carcinoma was evaluated by endorectal MRI approximately 4 months after the initiation of endocrine therapy in 48 patients with histolo gically confirmed prostate carcinoma detected by endorectal MRI before therapy. RESULTS. The volumes of the prostate gland, the carcinoma, a nd the noncarcinomatous components were reduced to 60.2 +/- 2.7%, 25.5 +/- 2.9%, and 83.2 +/- 6.3% of their pretreatment volumes respectivel y after endocrine therapy, indicating that the tumors are more suscept ible to endocrine therapy than the nontumorous components. The number of prostate carcinomas that demonstrated low signal intensity compared with the normal peripheral zone on T2-weighted images decreased after endocrine therapy and the number of carcinomas with enhancement of T1 -weighted contrast-enhanced images increased after therapy. Seven of t he 48 patients underwent downstaging after endocrine therapy, based on the endorectal MRI evaluation. CONCLUSIONS. The results of the curren t study suggest that downsizing and occasionally downstaging of the ca rcinoma may occur after endocrine therapy in patients with prostate ca rcinoma. In addition, the androgen sensitivity of the prostate carcino ma tissue is relatively high compared with the residual noncancerous p rostate gland. (C) 1997 American Cancer Society.