CT-guided radioactive ¹²⁵I seeds brachytherapy for lung oligometastases from colorectal cancer: initial results

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

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.

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.

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.