Co-planar template assisted CT guidance on the treatment of spinal metastases with ¹²⁵I seed implantation

Objective: To explore the quality control and the short-term curative efficacy of ¹²⁵I radioactive seeds implantation in the treatment of spinal metastases by using co-planar template(CPT) assisted CT guidance. Method: Totally 12 cases of primary tumor were diagnosed by pathology, imaging changes for 16 lesions were consistent with the characteristics of spinal metastatic tumor. The prescription dose (PD) was 80 Gy, seed activity was 1.48 × 10⁷ - 2.59 × 10⁷ Bq(0.4 - 0.7 mCi). According to preoperative plan, spinal metastases were treated with CPT assisted CT guided ¹²⁵I radioactive seeds implantation. The distribution of seeds was observed immediately after operation and the dose was assessed. Patients were followed up by CT to determine the change of tumor diameter and evaluate the efficacy. Follow-up time ranged from 3 to 29 months. And the improvement of pain was evaluated by pain grading. Results: All of the 16 spinal metastases lesions were successfully implanted by the preoperative planning. After the implantation, quality verification showed the average dose of target region was (209.21 ± 37.16)Gy, D₉₀(115.29 ± 7.87)Gy, D₁₀₀(76.59 ± 5.53)Gy, V₉₀(99.30 ± 0.51)%, V₁₀₀(98.06 ± 1.15)%, conformal index (CI) 0.981 ± 0.012, external index (EI) 0.012 ± 0.007. And the average dose of the spinal cord was (30.47 ± 4.83)Gy. There was no significant difference in the mean dose between the target area and the spinal cord and the preoperative plan (P > 0.05). 3 months after surgery, among 16 spinal metastases lesions, complete response (CR) was 18.8% (3/16), PR (partial response) rate 62.5% (10/16), PD(progressive disease) rate 6.25%(1/16), SD(stable disease) rate 6.25%(1/16), effective rate (CR + PR) 81.3%. The were 3 cases in pain complete remission, 7 cases in partial remission, 2 cases in mild remission. The survival time range from 11 to 39 months. The median survival time was 24 months. No radiation damage of spinal cord was found. Conclusions: CT guided CPT can be used to control the position and radiation dose of the seeds implantation before the operation, so as to achieve the objective of treating tumor with fewer complications and improvement of patients' tolerance. (authors)