Objectives: To evaluate the safety and effectiveness of computed tomography (CT)-guided radioactive ¹²⁵I seeds brachytherapy (RISB) for lung oligometastases (LO) from colorectal cancer (CRC).

Methods: Data for 144 LOs from 70 CRC patients who underwent CT-guided RISB were retrospectively analyzed. The primary endpoints were progression-free survival (PFS) and overall survival (OS), and the secondary endpoints were technical success, local control rate (LCR), and complications. Kaplan-Meier method was used for survival analysis. Cox model was used to identify the independent predictors of poor prognosis.

Results: The RISB procedures were successfully performed in all patients, and the success rate was 100%. The median follow-up was 27.8 months. The median PFS was 10.0 months (95% CI: 8.9-11.1) and the 1- and 2-year PFS rates were 32.9% and 5.9%, respectively. On multivariate analysis, serum carcinoembryonic antigen (CEA) ≤ 15 ng/ml (P = 0.048), middle-high differentiated pathological classification (P = 0.015), primary TNM stages I-III (P = 0.001), LO number ≤ 2 (P < 0.001) and cumulative gross tumor volume (GTV) ≤ 40 cm³ (P < 0.001) showed superior PFS. The median OS was 30.8 months (95% CI: 27.1-34.4) and the 1-, 2-, and 3-year OS rates were 95.7%, 67.4%, and 42.5%, respectively. On multivariate analysis, serum CEA ≤ 15 ng/ml (P = 0.004), middle-high differentiated pathological classification (P < 0.001), primary TNM stages I-III (P < 0.001), LO number ≤ 2 (P < 0.001), cumulative GTV ≤ 40 cm³ (P < 0.001) and system treatments combined with chemotherapy and target therapy (P < 0.001) showed superior OS. The LCR for 3, 6, and 12 months was 97.9%, 91.0%, and 83.6%, respectively. There were 4 cases of pneumothorax at 5.7% that required drainage.

Conclusions: RISB for LO from CRC is safe and effective, and serum CEA, TNM stage, LO number, cumulative GTV, and system treatments should be emphasized for long OS.