Early Indicators of Treatment Success After Percutaneous Radiofrequency of Pulmonary Tumors

Abstract

We retrospectively reviewed the imaging of patients after radiofrequency ablation (RFA) of lung metastases performed at our institution to assess the usefulness of ground glass opacification (GGO) margin for the prediction of complete tumor ablation. From January 2004 to March 2007, patients were identified where there was a postprocedure thin collimation scan to allow multiplanar reformatting, either immediately or at 24 h and at least 6 months of imaging follow-up. Thirty-six tumors in 22 patients were identified. The scans were assessed for the presence and width of GGO margin, and minimal and maximal dimensions were measured. A second reviewer, blinded to the outcome of the postprocedure assessment, reviewed the follow-up imaging for recurrence. The recurrence group had larger tumors (p = 0.045) and smaller mean minimal GGO margin width (p = 0.0001). Multivariate binary regression analysis confirmed that the minimal GGO margin was significantly (p < 0.005) associated with tumor recurrence. Receiver operator characteristic curve analysis suggests a cutoff of 4.5 mm for complete tumor ablation. There was substantial agreement (kappa = 0.759) between the site of absent GGO margin and the site of tumor recurrence. The point on the tumor surface where there is no GGO margin is likely to be the site of future recurrence. In our experience, a circumferential GGO margin of >5 mm is the minimal margion required to ensure complete tumor ablation.

Lung Adenocarcinoma: Predictive Value ofKRASMutation Status in Assessing Local Recurrence in Patients Undergoing Image-guided Ablation

“…Many predictors of tumor response after lung ablation have been proposed. Traditional predictors of local recurrence in PIA include tumor size and ablation margin (28)(29)(30). We saw a significant association between tumor size and local recurrence.…”

Lung radiofrequency and microwave ablation: a review of indications, techniques and post-procedural imaging appearances

“…It is well known that tumours may extend microscopically into the adjacent lung parenchyma by 6-8 mm, and it is therefore suggested that the ablation zone should be at least 1 cm larger than the lesion. 37,40,41 In an article by de Baère et al, 12 the ratio of post-treatment GGO to the pre-treatment tumour area was found to be predictive of success. If the ratio was at least four, the rate of complete ablation at 4 months was found to be 96%.…”

“…Although this can be short lived, it is a useful sign as if it encompasses the lesion with a satisfactory margin, there is good correlation with cell death and thus successful treatment. 12,37 Over a period of a week, the GGO usually changes to more dense airspace opacification. 38 GGO represents a transition from non-viable to viable tissue, and the outer margin of the shadowing probably overestimates the zone of complete ablation by 3-4 mm, emphasizing the need for an adequate treatment margin, analogous to the surgical margin in a resected tumour 39,40 ( Figure 2).…”

Standards of Practice: Guidelines for Thermal Ablation of Primary and Secondary Lung Tumors

“…The tumor tissue is considered to be incorporated in the ablation zone when the GGO completely surrounded the tumor [31,43]. The GGO should encounter the treated tumor with a circumferential margin of at least 5 mm for complete tumor ablation [44]. Other authors recommend that the area of postablation GGO should be 4 times the area of the tumor before ablation.…”