Comparison of clinical efficacy and complications of 125I seed brachytherapy and stereotactic body radiation therapy for recurrent pulmonary metastases from colorectal carcinoma

Abstract

Purpose: To evaluate the efficacies of ¹²⁵I seed implantation and stereotactic body radiation therapy (SBRT) in treatment of recurrent lung metastases from colorectal cancer, to compare the tolerance of lung tissue to both forms of radiotherapy, and to analyze the factors that affect the prognosis.

Material and methods: According to treatment received, thirty colorectal cancer patients with post-operative lung metastases were separated into two groups: ¹²⁵I seed implantation group (group A; n = 16) and SBRT group (group B; n = 14). Patients were followed up, and local control rate, survival, and post-operative complications were analyzed retrospectively. Kaplan-Meier method was used for survival analysis. Cox proportional hazards model was used to identify the independent predictors of poor prognosis.

Results: Survival was significantly different between group A and group B (median survival, 15 months and 11.5 months, respectively; p = 0.015). Local control rates at the first, third, sixth, and twelfth months after treatment were all > 80%, with no significant difference between the two groups (p = 0.829). Significant differences were seen between the two groups in the number of treatments received (p = 0.009) and the incidence of radiation pneumonitis (p < 0.001) as well as radiation-induced pulmonary fibrosis (p = 0.005). On multivariate regression analysis radiation pneumonitis was an independent predictor of poor prognosis (HR = 3.356, 95% CI: 1.518-7.421; p = 0.003).

Conclusions: ¹²⁵I seeds brachytherapy and SBRT are both effective for control of lung metastases but the former causes milder lung tissue damage. It can be repeated after short intervals, and appears to be a safe and efficient treatment for lung metastases.

Keywords: 125I seed; SBRT; colorectal cancer; efficacy; lung metastasis; survival analysis.

Fig. 1

Graph showing the diameters of all 73 lung metastases. A) The mean diameters of the metastases in the two groups were not significantly different. B) The risk of radiation pneumonitis increases with the increase in lesion diameter; the risk of grade 3 radiation pneumonitis is significantly higher when lesion diameter is ≥ 2 cm

Fig. 2

A 78-year-old woman had colon cancer resection. One year later, a metastatic lesion was found in the right upper lung. She was first treated with stereotactic body radiation therapy (SBRT). The top row shows the computed tomography (CT) images (a) before radiotherapy; (b) 4 months after SBRT; (c) 11 month after SBRT. Six months later, new lung metastatic nodules were found in the right lower lobe. SBRT could not be used because of radiation pneumonitis in the upper lobe of the right lung. Therefore, 125I seeds implantation was applied. The lower row shows the CT images (A) before treatment, (B) 2 months after treatment, and (C) 6 months after treatment. 125I seeds implantation and SBRT are both effective for control of lung metastases. However, the risk of radiation-induced lung injury is considerably lower with 125I seed implantation

Fig. 3

A 45-year-old woman was found to have a 9.1 mm in diameter metastatic nodule in the right upper lung 5 months after colon cancer resection. She was treated successfully with stereotactic radiotherapy (DT 50 Gy/5 Fx). A) Computed tomography (CT) before radiotherapy; arrow indicates the right upper lung metastatic nodule; B) 2 months after radiotherapy; the metastasis has reduced in size and shows decreased density; C) 4 months after radiotherapy; the lesion is blurred and there is a large groundglass opacity in the surrounding lung tissue; D) CT 6 months after radiotherapy; the region with the ground-glass appearance (irradiated area) contains recurrent metastatic nodules of about 11 mm in diameter. Local radiotherapy cannot be administered again because of the presence of radiation pneumonitis

Fig. 4

A 60-year-old man had recurrent right upper lung metastatic nodules 9 months after colon cancer resection and was successfully treated with 125I seeds implantation radiotherapy. The scout images (A0/B0/C0) acquired after seeds implantation (arrows). Computed tomography (CT) images of the chest at different levels show the right lower lung metastatic nodules (with diameters of 15/12/9 mm) before implantation. CT images 6 months after seeds implantation (A2/B2/C2) show disappearance of the metastatic nodules; residual artifact of the seed can be seen. CT images 10 months after seed implantation (A3/B3/C3) show small blurred areas around the seeds. A3 shows a recurrent pleural metastatic nodule (arrow) near the original one. Seeds implantation brachytherapy is being considered again for this recurrent metastatic nodule

Fig. 5

The survival rate of group A patients was significantly better than that of group B patients