Rates and Patterns of Recurrence After Microwave Ablation of Colorectal Liver Metastases: A Per Lesion Analysis of 416 Tumors in the Era of 2.45 GHz Generators

Prospective analysis of the effects of RAS mutation on local tumor progression and overall survival after radiofrequency ablation for colorectal liver metastases

OBJECTIVES

To investigate the effects of RAS mutation on local tumor progression (LTP) and overall survival (OS) after radiofrequency ablation (RFA) for colorectal liver metastases (CRLMs).

METHODS

This prospective study consecutively enrolled patients with CRLM who underwent ultrasound-guided RFA between June 2020 and July 2022. RAS mutation status was analyzed via the amplification refractory mutation system PCR method. The safety margin was measured via an anatomic landmark-based manual assessment method. Factors associated with time-to-LTP and OS were assessed via univariate and multivariate analyses.

RESULTS

A total of 163 patients with 284 ablated tumors were included. Sixty-nine patients (42.3%) had RAS mutations. Compared with the RAS-wild-type group, the RAS-mutant group had a higher 2-year cumulative LTP rate (20.0% vs. 9.8%, p = 0.016) and a worse 2-year OS rate (55.7% vs. 79.8%, p < 0.001). Compared with RAS-wild-type tumors, RAS-mutant tumors had a significantly greater 2-year cumulative LTP rate in the subgroups with safety margins <5 mm (47.6% vs. 24.9%, p = 0.034) and ≥5 mm (8.6% vs. 1.9%, p = 0.045). In the multivariate Fine-Gray analysis, RAS mutation (SHR, 2.42; p = 0.007) and a safety margin <5 mm (SHR, 7.94; p < 0.001) were found to be independent predictors of the time-to-LTP. According to the multivariate Cox analysis, RAS mutation (HR, 2.13; p = 0.010), CEA >5 ng/mL (HR, 2.29; p = 0.017), and extrahepatic metastases (HR, 2.04; p = 0.016) were independent predictors of shorter OS.

CONCLUSIONS

RAS mutation was an independent predictor of LTP and OS after RFA for patients with CRLM. RAS-mutant tumors require wider safety margins.

Contemporary Surgical Management of Colorectal Liver Metastases

Colorectal cancer is the third most common cancer in the United States and the second most common cause of cancer-related death. Approximately 20-30% of patients will develop hepatic metastasis in the form of synchronous or metachronous disease. The treatment of colorectal liver metastasis (CRLM) has evolved into a multidisciplinary approach, with chemotherapy and a variety of locoregional treatments, such as ablation and portal vein embolization, playing a crucial role. However, resection remains a core tenet of management, serving as the gold standard for a curative-intent therapy. As such, the input of a dedicated hepatobiliary surgeon is paramount for appropriate patient selection and choice of surgical approach, as significant advances in the field have made management decisions extremely nuanced and complex. We herein aim to review the contemporary surgical management of colorectal liver metastasis with respect to both perioperative and operative considerations.