PURPOSE: To evaluate the feasibility, efficacy, and safety of permanent 125I seed interstitial brachytherapy reirradiation in patients with ret~peritoneal lymph node recurrence under CT guidance.METHODS AND MATERIALS: Seventeen patients with 19 retroperitoneal lymph node recurrence after external beam radiotherapy underwent CT-guided 125I seed implant brachytherapy from October 2007 to August 2014.Treatment for all patients was preplanned using a three-dimensional radiation therapy planning system 3-5 days before brachytherapy;dosimetry verification was performed immediately after braehytherapy.RESULTS: The actuarial D90 (dose delivered to 90% of the target volume) was 100-198 Gy (median, 126.5 Gy).In 9 patients, pain intensity decreased to mild pain 1--3 weeks after brachytherapy.Pain-free survival ranged 2-15 months (median, 5 months;95% confidence interval [CI]: 0.1, 9.9).The overall response rate was 19 of 19 (100%).The median local control time was 15 months (95% CI: 2.3, 27.7).The 6-, 12-, and 24-month local control rate was 88.0%,63.2%, and 42.1%, respectively.Twelve patients (70.6%) developed distant metastases and died.Two patients (11.8%) are alive with distant metastases but no evidence of local recurrence.Three patients (17.6%) are alive with no evidence of local recurrence.Median overall survival was 10 months (95% CI: 5.7, 14.3);the 1-and 2-year survival rates were 38.1% and 15.3%, respectively.No major complications related to the procedure occurred during or after brachytherapy.CONCLUSIONS: Reirradiation with CT-guided permanent 125I seed interstitial brachytherapy is feasible, safe, and effective as pain relief or salvage treatment for patients with recurrent retroperitoneal lymph nodes.(C) 2015 American Brachytherapy Society.Published by Elsevier Inc.All rights reserved.