TRANSURETHRAL CS-137 MEDIUM DOSE-RATE RADIOTHERAPY AS A BOOST FOR SMALL-SIZED LOCALIZED PROSTATIC CARCINOMAS

The aim of this study is to present preliminary experience with Cs-137 medium dose rate (MDR) afterloading transurethral radiotherapy for sm all-sized (<2.5 cm) prostatic carcinomas. The phase II protocol compri ses 46 Gy of external beam radiotherapy, followed by two insertions (1 week apart) of Cs-137 MDR transurethral brachytherapy, each one deliv ering 8 Gy to a point 0.5 cm from the urethral walls. The treatment is completed with a 14-Gy boost to the prostatic area through lateral ex ternal beam fields. Up to now, 9 patients have been treated. The trans urethral insertion is a simple procedure, requires no anesthesia and t he ultrasonographic observation precisely and easily guided the positi oning of the applicator. Ah 9 patients are alive and disease-free 12-3 6 months after the end of radiotherapy. One of them presented a mild d egree of urethral stricture and none developed chronic proctitis or cy stitis. Seven patients were sexually potent before radiotherapy and al l of them maintained their potency. Transurethral radiotherapy for pro static carcinoma requires further investigation. The radiation dose th at the procedure delivers to the prostate is higher than the one presc ribed for external beam irradiation regimens. Rectal and bladder dose is substantially reduced, Although the prostatic urethra receives a hi gher dose, the incidence of urethral stricture is low probably because of the small tissue volume (8 cm(3)) in the high radiation dose area.