The accuracy and safety of CT-guided iodine-125 seed implantation assisted by 3D non-coplanar template for retroperitoneal recurrent carcinoma

PURPOSE: To investigate the accuracy, dosimetric parameters, and safety of 3D-printing non-coplanar template (3D-PNCT)-assisted CT guidance for radioactive iodine-125 (125I) seed implantation brachytherapy (RSI-BT) for retroperitoneal recurrent carcinomas METHODS AND MATERIALS: We enrolled 15 patients with 17 retroperitoneal recurrent carcinomas after external beam radiotherapy (EBRT). All patients received CT-guided 125I RSI-BT assisted by 3D-PNCT successfully. We compared the original needle insertion position, angular, and the needle tip distance deviations of preoperative plan with that of intraoperative in brachytherapy treatment planning system (B-TPS). The dosimetric parameters of RSI-BT were evaluated on preoperative plan, intraoperative real-time plan, and postoperative plan, including D90, D100 (the dose to 90% and 100% of the target volume), V100, V150, and V200 (the volume receives 100%, 150%, and 200% of the prescribed doses). The quality assurance of RSI-BT evaluated on conformal index (CI), external index (EI), and homogeneity index (HI) of the targets were compared among preoperative plan, intraoperative real-time plan, and postoperative plan. The perioperation complications and RSI-BT-related toxicity were assessed. RESULTS: The median follow-up was 8.2 months (range 1–18.5 months). One patient was lost to follow-up after RSI-BT. Fourteen patients were assessed for response rate and toxicity. The mean entrance point distance deviation for all 165 needles was 4.50 ± 4.10 mm (range, 0–30). The mean angular deviation was 2.70 ± 3.00° (range, 0–20). The needle tip distance deviation was 6.90 ± 6.00 mm (range, − 30–28). D90 for preoperative plan, intraoperative plan, and postoperative plan were 140.55 ± 23.93, 124.25 ± 28.04, and 128.98 ± 22.75, respectively. There was significant difference between D90 of preoperative plan with that of intraoperative plan (p = 0.036). Four lesions reached CR, six lesions reached PR, three lesions were SD, and three lesions were PD. Four patients with moderate pain became mild, and two with mild pain relieved completely after RSI-BT. The other parameters showed no differences among preoperative plan, intraoperative plan, and postoperative plan. The perioperative complications were observed in four patients, including three patients of grade 1 and one patient of grade 2. No ≥ grade 3 side effects were observed. CONCLUSION: CT-guided 125I RSI-BT assisted by 3D-PNCT was a safe, accurate, and feasible strategy for recurrent carcinomas located in the retroperitoneal regions.