Implications of radioactive seed migration to the lungs after prostate brachytherapy

To review the incidence and the impact of pulmonary seed migration after prostate brachytherapy on lung function. Isolated reports of seed migration to the lungs after prostate brachytherapy have been published; however, the clinical consequences of this pulmonary migration have not been adequately evaluated.

We performed a retrospective review of patients undergoing prostate brachytherapy from 1998 to 2000. Pulmonary imaging with chest x-ray was performed 15 to 90 days (median 45) after the procedure. The chest radiographs were reviewed by a single radiologist (V.S.D.), and patients with seed migration to the lungs were evaluated by a single pulmonologist (A.M.H.) using a questionnaire, chest radiography, and pulmonary function tests. Computed tomography of the prostate after seed implantation was performed to check seed position and dosimetry. Odds ratio, confidence intervals, chi-square tests, and logistic regression analysis were performed to evaluate the relationship between the type and number of seeds used, the incidence of pulmonary migration, and the effects on pulmonary function.

A total of 83 patients underwent prostate brachytherapy during the study period and 58 patients underwent chest radiography. Seed migration occurred in 21 (36.2%) of 58 patients (95% confidence interval 23.8% to 48.6%). Thirty-four (0.71%) of 4755 seeds used migrated to the lungs. Nine patients had single seed migration to the right lung and three to the left lung. Nine patients had multiple (maximum of 4) and bilateral seed migration. No consistent relationship was found between seed migration and the type of seeds used (P = 0.24). Borderline statistical significance suggested an increased incidence of seed migration with an increasing number of implanted seeds (P = 0.054). Repeat chest radiography in 21 patients revealed no delayed migration at a median follow-up of 16 months. Clinical and pulmonary function testing revealed no consistent abnormality attributable to seed migration.

Radioactive seed migration occurred in 36.2% of brachytherapy patients who had chest radiographs done in our series. Pulmonary seed migration may be influenced by the number of implanted seeds and does not appear to be influenced by the seed type. Additional study of this observed phenomenon is required. A thorough pulmonary workup failed to reveal any short-term harmful side effects; however, long-term follow-up is needed. Healthcare providers should discuss the possibility of pulmonary seed migration with patients with prostate cancer considering prostate brachytherapy.