Predictive Factors and Clinical Impact of Radioactive Seed Migration After Prostate Brachytherapy: A Retrospective Study

Radioactive seed migration after low-dose-rate brachytherapy (LDR-BT) for prostate cancer is a known phenomenon; however, its clinical impact remains unclear. We retrospectively analyzed 611 patients treated with LDR-BT using loose iodine-125 seeds. Post-treatment imaging was used to assess seed migration. Treatment efficacy was evaluated using post-plan dosimetry (V100 and D90) and biochemical recurrence-free survival (bRFS). Seed migration was observed in 150 patients (24.5%) within 1–3 months post-treatment, involving a total of 210 seeds. Migration sites included lungs, vasculature, and seminal vesicles. Hematogenous migration was significantly associated with higher seed counts. Seminal vesicle migration was linked to increased needle usage and absence of neoadjuvant hormone therapy. No significant differences were observed in V100, D90, or bRFS between patients with or without seed migration. However, migration of ≥3 seeds correlated with significantly lower V100 and with a trend toward decreased bRFS. Limited seed migration appears to have minimal clinical impact. However, ≥3 migrated seeds may reduce dosimetric quality and affect treatment efficacy. Risk factors include larger prostate volume as well as higher seed and needle counts. Improved planning and using linked seeds may reduce migration and improve outcomes in LDR-BT for prostate cancer.