Abstract: Objective To investigate the clinical efficacy, safety, and impact on survival of endobronchial ultrasound(EBUS)-guided iodine-125(¹²⁵I)seed implantation in patients with central lymph node metastases from lung cancer. Methods A total of 39 patients with central lymph node metastasis of lung cancer who underwent ¹²⁵I particle implantation guided by EBUS between 1, January 2021 and 1, November 2024 were selected for this study. The efficacy of the treatment was evaluated at one and three months after treatment on the target lesions. The diameters of the target lesions, karnofsky performance status(KPS)scores, carcinoembryonic antigen(CEA), neuron-specific enolase(NSE), and cytokeratin 19 fragments were compared before and three months after treatment. Subsequent chest CT reexamination at 3 months post-surgery resulted in the division of patients into two groups: stable disease(SD)cases were included in the stable group, while partial response(PR)and complete response(CR)cases were included in the remission group. The progression of the disease, survival rates, and mortality were the primary focus of the study. The survival differences between the stable group and the remission group were compared using the Log-rank test. Multivariate logistic regression analysis was performed to examine the correlation between recent efficacy and the dose delivered to 90% of the target volume(D90)post-surgery. Furthermore, multivariate Cox regression analysis was employed to identify independent factors affecting patient survival. Preoperative and postoperative symptoms, intraoperative adverse reactions, and postoperative complications were collated for the purpose of statistical analysis. Results Three months after the seed implantation procedure, local efficacy evaluations revealed a complete response(CR)in 7 patients(17.95%), a partial response(PR)in 13 patients(33.33%), stable disease(SD)in 19 patients(48.72%), and no progressive disease(PD), yielding an overall response rate(ORR)of 51.28% and a local control rate(LCR)of 100%. No occurrence of airway restenosis was observed at the target lesion site. Statistically significant differences were observed between baseline and 3-month post-treatment in tumor diameter(P<0.001)and KPS score(P<0.001). The follow-up period ranged from six to 12 months, with a median of 11 months. The progression-free survival(PFS)ranged from 3 to 12 months, the overall survival(OS)ranged from 3 to 12 months, and the survival rate was 69.23%. Log-rank analysis indicated higher survival in the response group than in the stable group, although the difference was not statistically significant(P=0.081). Multivariate logistic regression analysis revealed that postoperative D90 was higher in the response group than in the stable group(OR=1.115, 95%CI: 1.002-1.241, P=0.046), thereby identifying D90 as an independent factor influencing recent efficacy. Multivariate Cox regression analysis indicated that the number of prior treatment lines was an independent predictor of patient survival ［hazard ratio(HR)=0.181, 95%CI: 0.037-0.878, P=0.034］. During the procedure, 6 patients(15.38%)experienced puncture-site bleeding, which resolved after hemostatic treatment, and postoperative minor hemoptysis occurred in 3 patients(7.69%). No severe complications, such as radiation esophagitis, radiation-induced lung injury, or pericarditis, were observed during the follow-up period. Conclusion Patients with central lymph node metastases from lung cancer who undego EBUS-guided ¹²⁵I seed implantation achieves favourable short-term efficacy with minimal complications. Postoperative D90 is identified as an independent predictor of short-term efficacy and patients who attain complete or partial response have a better prognosis than those with stable disease. The number of treatment lines is an independent determinant of patient survival.

Key words: Iodine-125 seed, Endobronchial ultrasound-guided, Intraoperative implantation, Lung cancer, Lymph nodes