A randomized trial comparing seed displacement of coated seeds to regular loose seeds at 30 days postimplant

To compare 30-day seed displacement and seed loss of standard loose seeds to specially engineered coated seeds.

Forty patients with prostate cancer were randomized and treated with either loose seeds or loose "coated" seeds. Implants were preplanned using transrectal ultrasound and performed using preloaded needles containing either standard or coated iodine-125 seeds according to randomization. Pelvic X-rays and CT were performed on Days 0 and 30 and a pelvic magnetic resonance scan on Day 30. Cranial-caudal displacement relative to the center of mass (COM) of the seed cloud of the six most peripheral basal and apical seeds was determined from Day 0 and 30 CT scans using custom software. Day 30 magnetic resonance-CT fusion was performed using a seed-to-seed match for soft tissue contouring on MRI.

The mean displacement for the six basal seeds was 0.32 cm (standard deviation [SD], 0.25 cm) and 0.33 cm (SD, 0.27 cm) toward the COM for the regular and coated seeds, respectively (p = 0.35). For the apical seeds, mean displacement was 0.31 cm (SD, 0.35 cm) and 0.43 cm (SD, 0.26 cm) (p = 0.003) toward the COM. More regular seeds (n = 8) were lost from the apical region as compared with one coated seed (p = 0.015). There was a trend to reduction in total seeds lost: 1% for regular seeds as compared with 0.3% for coated seeds.

Coated seeds were found to have a significant anchoring effect that was effective in reducing the number of apical seeds lost because of venous migration.