3D Quantitative Ablation Margins for Prediction of Ablation Site Recurrence After Stereotactic Image-Guided Microwave Ablation of Colorectal Liver Metastases: A Multicenter Study

Abstract

BackgroundThree-dimensional (3D) volumetric ablation margin assessment after thermal ablation of liver tumors using software has been described, but its predictive value on treatment efficacy when accounting for other factors known to correlate ablation site recurrence (ASR) remains unknown.PurposeTo investigate 3D quantitative ablation margins (3D-QAMs) as an algorithm to predict ASR within 1 year after stereotactic microwave ablation (SMWA) for colorectal liver metastases (CRLM).Materials and MethodsSixty-five tumors in 47 patients from a prospective multicenter study of patients undergoing SMWA for CRLM were included in this retrospective 3D-QAM analysis. Using a previously developed algorithm, 3D-QAM defined as the distribution of tumor to ablation surface distances was assessed in co-registered pre- and post-ablation CT scans. The discriminatory power and optimal cutoff values for 3D-QAM were assessed using receiver operating characteristic (ROC) curves. Multivariable logistic regression analysis using generalized estimating equations was applied to investigate the impact of various 3D-QAM outputs on 1-year ASR while accounting for other known influencing factors.ResultsTen of the 65 (15.4%) tumors included for 3D-QAM analysis developed ASR. ROC analyses identified i) 3D-QAM <1 mm for >23% of the tumor surface, ii) 3D-QAM <5 mm for >45%, and iii) the minimal ablation margin (MAM) as the 3D-QAM outputs with optimal discriminatory qualities. The multivariable regression model without 3D-QAM yielded tumor diameter and KRAS mutation as 1-year ASR predictors. When adding 3D-QAM, this factor became the main predictor of 1-year ASR [odds ratio (OR) 21.67 (CI 2.48, 165.21) if defined as >23% <1 mm; OR 0.52 (CI 0.29, 0.95) if defined as MAM].Conclusions3D-QAM allows objectifiable and standardized assessment of tumor coverage by the ablation zone after SMWA. Our data shows that 3D-QAM represents the most important factor predicting ASR within 1 year after SMWA of CRLM.

Intraprocedural Versus Initial Follow-up Minimal Ablative Margin Assessment After Colorectal Liver Metastasis Thermal Ablation

“…Previous studies have used rigid and nonrigid image registration methods to assess the MAM and have reported various optimal cutoff values for MAM to minimize LTP, ranging from 2 to 5 mm. 6,7,12 In this present study, we found that no LTP was noted with an MAM of more than 3.2 mm on intraprocedural CT, which was consistent with previous studies including one from our group that used the same ablation confirmation methodology. 3 However, a cutoff value of 5 mm on MAM quantified on initial follow-up CTwas not a significant predictor for LTP.…”

“…1,2 Further, sufficient ablative margin is considered as a critical factor for local tumor control, and several dedicated ablation confirmation methods have been developed to standardize the process of ablative margin quantification. [3][4][5][6][7] Recently, an ablation confirmation method using biomechanical deformable imaging registration method, which takes into consideration the liver's biomechanical properties and deformation after ablation, has been proposed. This method disclosed that a minimal ablative margin (MAM) of ≥5 mm was achieved in less than half of tumors that were ablated with an endpoint of margin ≥5 mm evaluated by visual inspection in a retrospective analysis.…”

“…Guidelines have recommended that thermal ablation can be used alone or in conjunction with surgery if all visible disease can be eradicated 1,2 . Further, sufficient ablative margin is considered as a critical factor for local tumor control, and several dedicated ablation confirmation methods have been developed to standardize the process of ablative margin quantification 3–7 . Recently, an ablation confirmation method using biomechanical deformable imaging registration method, which takes into consideration the liver's biomechanical properties and deformation after ablation, has been proposed.…”

Real-Time Split-Dose PET/CT-Guided Ablation Improves Colorectal Liver Metastasis Detection and Ablation Zone Margin Assessments without the Need for Repeated Contrast Injection

“…The limited number of PET/CT scanners worldwide and the even smaller number of dedicated PET/CT equipment allowing the presence of anesthesia equipment and staff for image-guided interventions currently impact the utility of this method in most institutions [ 21 ]. Although 3D software is increasingly used and is recommended for the proper assessments of the AZ [ 8 , 34 , 35 ], its widespread availability is still lacking. All software platforms are affected by motion artifacts and extreme positioning differences that impact registration and fusion.…”

Comparison of Two 2.45 GHz Microwave Ablation Devices with Respect to Ablation Zone Volume in Relation to Applied Energy in Patients with Malignant Liver Tumours

“…The most important drawback of thermal ablation is the appearance of viable tumour tissue at the edge of the ablation zone [ablation site recurrence (ASR)] [ 10 , 11 ]. Complete tumour coverage with an adequate ablation margin assessed in 3D is crucial for treatment success [ 12 , 13 , 14 , 15 ]. To achieve complete tumour coverage, creation of predictable ablation volumes is essential and depends, among other things, on the applied energy controlled by the power and time setting of the ablation device.…”