The efficacy and safety of CT-guided 125I seed implantation by coplanar template as a salvage therapy for vertebral metastases after failure of external beam radiation therapy: a retrospective study

Abstract Purpose To evaluate the efficacy and safety of computed tomography (CT)-guided 125I seed implantation by coplanar template for vertebral metastases after failure of external beam radiation therapy. We also want to compare the dosimetry of 3D printed coplanar template-assisted interstitial 125I brachytherapy preoperative and postoperative, and to explore the accuracy of this technology. Material and methods We retrospectively collected and analyzedthe results of 56 patients with vertebral metastases after failure of external beam radiation therapy, who underwent interstitial 125I brachytherapy as a salvage treatment with a CT-guided coplanar template-assisted technique from January 2015 to January 2017. Results The NRS score for worst pain was 6.1 ± 1.1 before 125I seed implantation. The mean posto-perative NRS score decreased significantly at T4w (3.5 ± 0.9, p < 0.01), T8w (2.1 ± 0.9, p < 0.01), T12w (1.5 ± 0.7, p < 0.01) and T6m (1.2 ± 0.6, p < 0.01) respectively. There was no significant difference in scores among T0, T24h (P = 0.10) and T1w (P = 0.09). The local control rates after 3, 6, 9 and 12 months were 100% (58/58), 92.5% (49/53), 90.2% (46/51), and 85.1% (40/47), respectively. By performing paired t-test analysis, there were no significant differences in D90, D100, V90, V100, V150, V200, GTV volume, CI, EI and HI between preoperative and postoperative(p༞0.05). Postoperative D90 was an independent influencing factor of local control time (HR: 1.047, 95% CI: 0.998–1.098, p = 0.043). The optimal Cut-off value of postoperative D90 was 130 Gy. Conclusions Interstitial 125I seed implantation can be used as a salvage treatment forpatients with vertebral metastases after failure of external beam radiation therapy. With the auxiliary function of 3D printed coplanar template, the main dosimetry parameters verified after the operation can meet the requirements of the preoperative plan with good treatment accuracy.