The accuracy and dosimetric analysis of 3D-printing non-coplanar template-assisted iodine-125 seed implantation for recurrent chest wall cancer

Introduction
To investigate the accuracy and dosimetry of 3D-printing non-coplanar template (3D-PNCT)-assisted computed tomography (CT)-guided iodine-125 seed implantation (125I-SI) for recurrent chest wall cancer (rCWC).

Material and methods
This was a retrospective study of 19 patients with 22 rCWC treated with 3D-PNCT-assisted CT-guided 125I-SI, from Mar 2017 to Mar 2020 in our institute.

Results
Mean needle entrance deviation was 4.50 ±2.70 mm, mean angular deviation was 3.40 ±3.10 degrees, and mean depth deviation was 5.20 ±5.20 mm. No significant difference was found for dosimetric parameters (except conformity index) between pre-plan and post-plan; D90, D100, V100, V150, and V200 were 157.74 ±24.23 and 151.71 ±33.62 (p = 0.228), 85.36 ±34.09 and 70.46 ±23.48 (p = 0.067), 0.93 ±0.04 and 0.90 ±0.07 (p = 0.068), 0.64 ±0.16 and 0.64 ±0.16 (p = 0.984), and 0.35 ±0.17 and 0.37 ±0.18 (p = 0.382) for pre-plan and post-plan, respectively. Conformity index, external index, and homogeneity index were 0.57 ±0.16 and 0.52 ±0.15 (p = 0.007), 0.73 ±0.55 and 0.79 ±0.53 (p = 0.096), and 0.31 ±0.15 and 0.30 ±0.14 (p = 0.504) for pre-plan and post-plan, respectively. Median follow-up time was 8 months (range, 3-30 months). Complete response was observed in 4/22 (18.1%), partial response in 13/22 (59.1%), stable disease in 4/22 (18.1%), and progression disease in 1/22 (4.5%) of the cancers. Among patients with pain before 125I-SI, pain relief rate was 87.5% (7/8). No peri-operative complications of more than grade 2 were observed.

Conclusions
3D-PNCT-assisted CT-guided 125I-SI may be safe and feasible as palliative therapy for non-surgical candidates and painful patients with rCWC.