Reduction of pulmonary migration of permanent interstitial sources in patients undergoing prostate brachytherapy

Objectives. To investigate a method to decrease the problem of seed migration after permanent prostate brachytherapy. Permanent prostate brachytherapy can be performed by a number of techniques using several different seed configurations. All have been associated with some degree of pulmonary seed migration, and no studies have clearly investigated a means of decreasing this problem. Methods. A total of 238 patients underwent implantation with either iodine-125 (I-125; 146 patients) or palladium-103 (92 patients). The implant was performed in real time using an applicator, with the sources placed just underneath the prostatic capsule. Postimplant dosimetry was performed at 1 month. Routine chest x-ray was obtained a minimum of 4 months after implantation; 24 patients had a second chest x-ray taken. Results. A total of 21,654 seeds were implanted (median 89, range 27 to 220). Postimplant chest x-rays were obtained at a median of 912 days (range 147 to 3023), and 4 patients (1.7%) experienced at least one seed embolus to the lung. Of the 21,654 seeds, 10 (0.005%) were found in the lungs. All 4 patients had received an I-125 implant, resulting in a pulmonary embolus rate for I-125 of 2.7% (4 of 146) and for palladium-103 of 0% (0 of 92). No patients experienced subsequent seed migration if it was not seen on the initial film. The median dose delivered to 90% of the prostate volume for all patients undergoing I-125 implantation was 172 Gy and for the 4 patients with seed migration it was 174 Gy. Conclusions. Seed embolism to the lungs is a rare event when patients undergo implantation using the real-time method. Although in our series migration was slightly greater with I-125 than with palladium-103, no negative effect was seen on the postimplant dosimetry results.