Brachytherapy in patients with small prostate glands.

Abstract

Purpose: To better define the role of small prostate volume in selecting patients for brachytherapy.

Materials and methods: Thirty patients with a transrectal ultrasound (TRUS)-based prostate volumes less than 20 cc were treated at the University of Washington by permanent isotope implantation for prostatic carcinoma. Preimplant TRUS studies were taken at 0.5-cm intervals from the base of the gland to the apex. Planning margins of 1 to 5 mm were added to the prostatic margins, and sources were routinely planned to be placed as much as 5 mm outside of the prostatic margin. The prescription dose was 144 and 115 Gy for full-dose iodine 125 and palladium 103 monotherapy, respectively. For patients receiving supplemental external-beam irradiation, the implant doses were 120 and 90 Gy for 125I and 103Pd, respectively. The morning following the implant, axial computed tomographic (CT) images of the prostate were obtained at 0.5-cm intervals with patients in the supine position. Follow-up ranged from 11 to 28 months (median 21 months).

Results: The median coverage of the postimplant prostate volume by the prescription dose was 92%. To calculate the incidence of source migration, the number of sources placed at the time of implant was compared with the number identified on postimplant CT scan. The median number of sources implanted was 84 (range 65-103) compared to an average of 82 identified postoperatively, which is consistent with a source migration rate of two. A median of 31 sources appeared to be outside of the prostatic margins, as identified on postimplant CT scan (range 14-53). Of the 23 patients contacted at the time of this report, one had developed acute postimplant urinary retention that resolved within 2 weeks of implantation. At last follow-up, patient pre- and postimplant AUA scores were not substantially different, with the median AUA score increasing from 7 (range 2-21) to 8 (range 1-27).

Conclusions: Patients with small prostate volumes appear to have acceptable morbidity and target coverage with prostate brachytherapy. Based on the data reported here, we do not believe that a small prostate volume in itself is a contraindication to brachytherapy.