The effect of supplemental beam radiation on prostate brachytherapy-related morbidity:: Morbidity outcomes from two prospective randomized multicenter trials

Abstract

Purpose To detail the effect of supplemental beam radiation on prostate brachytherapy-related morbidity. Methods and materials The 220 patients reported here were a subgroup randomized on two treatment protocols, with a planned total accrual of 1200. Low-risk patients, with Gleason Grade 2–6, prostate-specific antigen (PSA) 4–10 ng/mL, were randomized to implantation with I-125 (144 Gy, TG-43) vs. Pd-103 (125 Gy, NIST-99). Intermediate-risk patients, with Gleason Grade 7 or higher or PSA of 10—20 ng/mL, were randomized to implantation with Pd-103, delivering 90 vs. 115 Gy (NIST-1999), with 44 vs. 20 Gy external beam irradiation (EBRT), respectively. Beam radiation was delivered with a four-field arrangement, designed to cover the prostate and seminal vesicles with a 2-cm margin (reduced to 1.0 cm posteriorly). Treatment-related morbidity was monitored by mailed questionnaires, using standard American Urologic Association (AUA) and Radiation Therapy Oncology Group criteria at 1, 3, 6, 12 and 24 months. Use of alpha-blockers to relieve obstructive symptoms was not controlled for, but was noted at each follow-up time. Results AUA score increases were highest at 1 month in the patients treated with higher prescription doses of Pd-103 (125 Gy Pd-103 alone or 115 Gy Pd-103 with 20 Gy EBRT), consistent with prior reports. By 6 months, most Pd-103 patients had returned to baseline, whereas I-125 patient scores were still declining. Patients treated with lower dose Pd-103 combined with EBRT had lesser elevations of their AUA scores at 1 and 6 months, but differences between those receiving 20 vs. 44 Gy beam radiation were inconsistent. At no point did beam radiation significantly affect postimplant AUA scores or urinary morbidity scores. Rectal morbidity scores were remarkably similar between groups, apart from higher scores at 1 month in patients treated with full dose Pd-103. Rectal morbidity consisted primarily of increased frequency and mucous passage. There have been no instances of rectal ulceration or fistula. The addition of beam radiation significantly increased postimplant rectal morbidity scores only at the 1-month time point. Conclusion The addition of supplemental beam radiation had little effect on morbidity. We do not believe that morbidity per se should influence the decision of whether or not to use supplemental beam radiation.