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.