First report on the use of a thinner (125)I radioactive seed within 20-gauge needles for permanent radioactive seed prostate brachytherapy: evaluation of postimplant dosimetry and acute toxicity.

To compare postoperative dosimetry and acute toxicity of new 0.5-mm (125)I seeds in 20-gauge (20G) diameter prostate brachytherapy (PB) needles with standard 0.8-mm seeds in 18G needles.Postoperative dosimetry was performed on 100 consecutive PB patients treated with ThinSeeds in 20G needles and compared with 100 consecutively treated PB patients using standard-sized seeds and needles (18G). Dosimetry was performed on postoperative Day 1 CT scans. Acute urinary retention was also compared between these two groups. Acute toxicity was evaluated in 22 consecutively treated patients with thinner seeds/needles and compared with 22 consecutive concurrent patients treated with standard seeds and needles. All patients were evaluated by pre- and post-PB self-administered surveys, physical examinations on post-PB Day 1, and telephone surveys on Day 7. Endpoints included dysuria, acute urinary retention, hematuria, perineal pain/bruising, and International Prostate Symptom Score.Post-PB dosimetric comparison demonstrated that the V100 (95% vs. 91%), D90 (161Gy vs.149Gy), V150 (55% vs. 45%), and RV100 (0.43cc vs. 0.30cc) were significantly (p<0.0004) higher in the 20G group. Urinary retention rates were 8% and 7% and median catheter-dependent durations were 7 and 14 days for the 20G and 18G groups, respectively. No significant differences were found for dysuria, hematuria, or International Prostate Symptom Score. Post-PB Day 1 perineal bruising and pain scores on Days 1 and 7 were significantly less (p<0.04) in 20G cohort.Smaller diameter needles and seeds resulted in improved post-PB Day 1 V100 and D90 dosimetry, and significantly less acute perineal pain and bruising.