To evaluate the efficacy of ¹²⁵I seed implantation and stereotactic body radiation therapy (SBRT) in the treatment of lung metastases postoperative resection of colorectal cancer, to compare the tolerance of lung tissue to both radiotherapy, and to analyze the factors that affect the prognosis.

Thirty-six colorectal cancer patients with postoperative lung metastases were divided into two groups according to the treatment, ¹²⁵I seed implantation group (group A, n=20) and SBRT group (group B, n=16) . Patients were followed up, and the local control rate, survival rate, and postoperative complications were analyzed retrospectively. Kaplan-Meier method was used for analysis of survival rate. Cox proportional hazards model was used to identify the independent predictors of poor prognosis and to analyze the prognostic factors.

Survival rate had no significant difference between groups A and B (median live time of 15 months and 13 months, respectively; Log-Rank χ²=1.131, P=0.440) . Local control rates after 1, 3, 6 and 12 months of treatment were all >80%, with no significant difference between the two groups (P=0.897) . The incidence of radiation-induced lung injury in group B was higher than that in group A, with significant differences between the two groups in the number of recurrent treatments [ (2.35±0.58) times vs. (1.69±0.48) times, t=3.729, P=0.001], the incidence of radiation pneumonia (P<0.001) and radiation-induced pulmonary fibrosis (P=0.004) . Multivariate regression analysis showed that radiation pneumonitis was an independent predictor of poor prognosis (HR=2.213, 95%CI: 1.013-4.834, P=0.046) .

Compared with SBRT, ¹²⁵I seeds brachytherapy can be repeated within a short time, and causes milder lung tissue damage. The treatment of pulmonary metastasis is safe and effective, and the clinical application is less limited.