To prospectively observe imaging features and local control of advanced lung tumors after radiofrequency ablation (RFA), and to propose a follow-up protocol post-ablation. 58 stage IV malignant lung tumor patients were enrolled in our study. One hundred of lung lesions were performed 77 sessions of RFA. Enhanced computed tomographic (CT) images of pre-ablation, 1-month, and 3-month post-ablation and thereafter every 3 months were obtained. Positron emission tomographic/CT (PET/CT) was performed pre-ablation, 3-month post-ablation and thereafter every 6 months. The CT size, shape, enhancement, and PET/CT metabolic activity of the ablated zone were analyzed to assess local lesion control. There was significant difference in lesion size between pre-ablation and 1-month post-ablation (P=0.000), 1 and 3-month post-ablation (P=0.000), 3 and 6-month post-ablation (P=0.006). Metabolic activity of the ablated zone after 3 months decreased markedly as compared with pre-ablation (p=0.001). Local control rate was 88%, and forms of definite recurrence or residual included increased size, nodular enhancement, and central enhancement. Time to local progression (TTLP), progression-free survival (PFS), and overall survival (OS) were 15.4±7.5, 9.6±5.8 and 18.0±7.0 months respectively. No death related to operation occurred, and the main complication rate was 29%, of which 9% needed clinical management. RFA is a safe and effective approach for local control of lung tumors even if in advanced patients. To obtain definite CT evaluation, lesion size at 1-month post-ablation as the baseline is appropriate, with efficacy assessment 6-month post-ablation. PET/CT is a useful tool to predict recurrence or residual at least 3 months post-ablation.
Keywords: Radiofrequency ablation; advanced lung tumors; follow-up protocol; imaging features; local control.