How many times 125I seed implantation brachytherapy can be repeated for pulmonary metastases: clinical efficacy and complications

Purpose: The aim of the study was to determine how many times iodine-125 (125I) seed brachytherapy (ISB) for recurrent pulmonary metastases (RPM) can be done, and the clinical efficacy and complications of repeated ISB in RPM treatment. Material and methods: Between September 2013 and August 2018, 18 patients with RPM, after conventional chemotherapy, radiotherapy, and trans-arterial chemoembolization, received CT-guided repeated ISB. Patients were followed up, and local control, survival, and post-operative complications were analyzed retrospectively. The Kaplan-Meier method was used for survival analyses. Results: Eighty-two metastases in 18 patients were treated with ISB, with 71 implantations (mean number of implantations per patient, 4; range, 3-8). The total number of implanted 125I seeds was 1,220 (mean number per patient, 68; minimum, 40; maximum, 110). The mean value of D90 for ISB was 138 Gy. Local control was 91.46%, 90.24%, and 89.02% at 1, 3, and 6 months after ISB, respectively. After repeated ISB, good local control was achieved, and all patients were discharged from hospital within 3 days. One month after, six metastases of large diameter were treated with ISB; computed tomography revealed level 1 radioactive injury to the lungs, but special treatment was not administered. Post-operative renal, hepatic, and vascular functions were normal. Conclusions: ISB for RPM is safe and efficacious. RPM treatment seems not to be limited by number of times ISB could be repeated; at least up to 8 times for different sites of lung.