Predictive Factors for Local Recurrence after Intraoperative Microwave Ablation for Colorectal Liver Metastases

SIMPLE SUMMARY: The European Society of Medical Oncology and National Comprehensive Cancer Network guidelines indicate that ablation is recommended as a stand-alone treatment or in combination with resection for colorectal liver metastases (CRLM) as long as all visible tumors are eradicated. However, local recurrence (LR) is a major setback for microwave ablation (MWA). Even though several LR predictors have been reported, those following intraoperative MWA still remain unclear. Therefore, we retrospectively analyzed CRLM cases to determine LR predictive factors following intraoperative MWA. The minimal ablation margins were measured using anatomic landmarks, and a multivariate analysis for LR predictors after intraoperative MWA revealed that the ablation margin was the most powerful predictor per patient and lesion. In addition, anatomical location (i.e., the posterosuperior segment defined as segments 1, 7, and 8), tumor size >15 mm, tumor size > 20 mm, and proximity to Glisson were the independent LR predictors per lesion. ABSTRACT: This study aimed to clarify local recurrence (LR) predictive factors following intraoperative microwave ablation (MWA) for colorectal liver metastases. The data from 195 patients with 1392 CRLM lesions, who were preoperatively diagnosed by gadolinium-enhanced MRI with diffusion-weighted imaging and dynamic CT and treated with intraoperative MWA (2450 MHz) with or without hepatectomy, from January 2005 to December 2019, were retrospectively reviewed and analyzed using logistic regression. In addition, the margins were measured on contrast-enhanced CT 6 weeks post-ablation. Overall, 1066 lesions were ablated. The LRs occurred in 44 lesions (4.1%) among 39 patients (20.0%). The multivariate analysis per patient showed that tumor size > 20 mm and ablation margin < 5 mm were significant predictors for LR. Furthermore, multivariate analysis per lesion revealed that segments 1, 7, and 8 and tumor size > 15 mm, ablation margin < 5 mm, tumor size > 20 mm, and proximity to the Glisson were significant LR predictors. Finally, the outcome of this study may help determine indications for MWA.