Dosimetric Analysis Of Urinary Morbidity Following Prostate Brachytherapy (I-125 Vs. Pd-103) Combined With External Beam Radiation Therapy

The purpose of this analysis was to correlate isotope selection with the urinary symptoms of patients who received a combination of external beam radiotherapy (EBRT) and a transperineal interstitial permanent prostate brachytherapy (TIPPB) boost with either a (103)palladium (Pd-103) or a (125)iodine (I-125) radioisotope. Postimplant dosimetry was performed to evaluate both urethral dose and implant quality. The American Urologic Association (AUA) scores in both the I-125 and Pd-103 groups were similar initially. However, at 1, 3, 6, and 12 months of follow-up, the mean AUA scores for the I-125 and Pd-103 patients were 18 6 vs. 11 9, 17 7 vs. 117, 10 3 vs. 9 4, and 14 8 vs. 7 5, respectively (P < 0.01). The only significant difference between the postimplant dose-volume histogram (DVH) of the I-125 and Pd-103 implants was the minimum dose that 90% of the urethra received (D-90). The increased AUA score of the I-125 group was weakly correlated (R-2 = 0.20) with the D-90 dose but that of the Pd-103 patients was not (R-2 = 0.00). This suggests that the higher AUA score of the 1251 patients was not necessarily the result of the higher D-90 dose. Thus, patients who received Pd-103 experienced less urinary morbidity than those implanted with I-125. We recommend further validating these findings in prospective studies in which the quality of the I-125 and Pd-103 implants can be evaluated. (C) 2002 Wiley-Liss, Inc.