Improvements in prostate brachytherapy dosimetry due to seed stranding

Purpose: Prostate brachytherapy with suture embedded seeds has emerged as a popular technique to reduce seed migration and to improve dosimetry. Various trials have shown improved dosimetry with seed fixity, whereas others have shown no benefit and possible detriment to suture embedded seeds. In order to contribute to the understanding of whether seed stranding improves dosimetry, we present retrospective data from our institution. Methods and materials: We analyzed 80 patients treated between April 29, 2001 and June 19, 2006, receiving I-125 monotherapy for prostate cancer. Brachytherapy patients at the University of California, Los Angeles (UCLA) were initially treated using a transperineal approach with loose seeds. Subsequent to October 26, 2002, all patients were implanted using suture embedded seeds. Dosimetric quantifiers were calculated based on a CT obtained 1-month postimplantation. Results: Dosimetry of patients treated with stranded seeds showed significant improvement. Specifically, the V100 (volume of the prostate receiving 100% of the prescribed dose) improved from 88% to 92% (p <0.05), and the D90 (maximum dose received by 90% of the prostate) improved from 143 to 155 Gy (p <0.05). Conclusions: At UCLA, the use of suture embedded seeds resulted in a significant improvement in our dosimetric quantifiers. Based upon other published studies, this improvement in dosimetry may translate into improved patient outcomes.