Prostate brachytherapy seed migration and dosimetry: analysis of stranded sources and other potential predictive factors

Purpose The purpose of this study was to evaluate the influence of potential contributing factors to the incidence of seed migration and quality of prostate brachytherapy dosimetry. Methods and materials Sixty patients were evaluated with day one and 3–12 month plain films of the pelvis and chest, and day 1 CT-based dosimetry analysis. The incidence and types of seed migration were quantified. The seed migration outcome was evaluated with respect to source type (free vs. stranded), prostate volume, number of seeds, and needles. The day one prostate V100, V150, D90, and urethra D10 outcomes were evaluated with respect to source type, radiation type (125I vs. 103Pd), prostate volume, prostate swelling, and quantity of migrating seeds. Results An increased incidence of day one and cumulative seed migration was predicted by free vs. stranded source type, with a relative risk of 6.97 and 3.08, respectively. Pulmonary and distal (toward the perineum) migration patterns were significantly reduced in the stranded group. An increased day one prostate V100, V150, D90, and urethra D10 outcome was predicted by stranded source type. Conclusion Stranded source type was associated with decreased seed migration as well as higher prostate and urethra dosimetry values, resulting in an implant in which more radiation resided within the target volume, and less radiation metastasized to undesirable locations.