HIGH-DOSE-RATE AFTERLOADING (192)IRIDIUM PROSTATE BRACHYTHERAPY - FEASIBILITY REPORT

Background: Results from localized prostate cancer series using seed i mplants have been most encouraging. However, with current techniques,i nadequate dosimetry sometimes occurs. Remote afterloading high dose ra te (192)Iridium brachytherapy (HDR-Ir192) theoretically remedies some potential inadequacies of seed implantation by performing the dosimetr y after the needles are in place. This study was undertaken to determi ne the feasibility of incorporating multifractionated HDR-Ir192 in the brachytherapy management of prostate carcinoma. Methods: From October 1989 to August 1995, 104 patients were treated with a combination of multifractionated HDR-Ir192 and external beam. Patients ranged in age from 48-78 years, with a mean of 68.6 years. By TNM clinical stage, th ere were 1 T1b, 31 T1c, 28 T2a, 24 T2b, 9 T2c, 8 T3a, and 3 T3c lesion s. For the group, the mean initial pretreatment PSA was 12.9 ng/ml (me dian 8.1), with 90% of the patients having had a pretreatment PSA grea ter than a normal value of 4.0 ng/ml. Patients with prostate volumes u p to 105 cc were implanted. Treatment was initiated with perineal need le placement using ultrasound guidance. A postoperative CT scan was ob tained to provide the basis for treatment planning. Four HDR-Ir192 tre atments were given over a 40-h period, with a minimal peripheral dose (MPD) ranging from 3.00 to 4.00 Gy per fraction over the course of thi s study. Two weeks later, external beam radiation was added using 28 f ractions of 1.80 Gy daily, to a dose of 50.40 Gy. Results: Follow-up r anged from 10 to 89 months, with a mean of 46 months and median of 45 months. At various follow-up points, the patient numbers at risk were: 1 year, 101; 3 years, 69; 5 years, 28. The technique proved to be uni formly applicable to a wide range of prostate volumes and was very wel l tolerated by patients. Nearly all significant late in-field treatmen t complications were genitourinary in nature. Of the patients, 6.7% de veloped urethral strictures that were readily manageable. Changes in t echnique implemented in 1993 appear to have significantly lessened the incidence of this complication. Two patients developed significant ur opathy within the first treatment year, but bath resolved; 1 of these 2 patients had a prior TURP. Other. bladder or rectal complications ha ve been minimal. Using PSA progression as a marker of tumor response, approximately 84% of patients whose initial PSA was less than 20 ng/ml were free of progression at 5 years by actuarial analysis. Conclusion s: We found the use of transperineal ultrasonography, postimplant CT-b ased dosimetry, coupled with adjustable dose delivery inherent to remo te afterloading technology, to give unparalleled control in performing this complex brachytherapy task. Thus, it may be advantageous in cert ain clinical situations where the resultant MPD is needed to reliably cover the target volume, such as in patients with carcinomas at base l ocales, when the possibility of moderate to extensive intraprostatic t umor exists, and in patients with large glands. Early PSA data suggest that it may be effective as a definitive treatment with rates of-adve rse late tissue effects that are acceptable using current technique an d doses described herein. Longer follow-up is needed to ascertain its position among the various treatment regimens for prostate carcinoma. (C) 1998 Elsevier Science Inc.