Surgical microwave ablation for multifocal non-resectable liver metastases: a single institution experience treating five or more liver lesions

Background: Thermal ablation is an effective treatment for patients with metastatic colon and rectal cancer and allows surgeons to offer curative intent therapy to patients who are otherwise not candidates for resection. We aimed to report outcomes of a single institution experience using microwave ablation (MWA) with or without resection to treat five or more liver metastases. Methods: In this retrospective cohort study, the University of Minnesota Division of Surgical Oncology liver surgery database was queried to identify all patients who underwent thermal ablation of five or more colorectal liver metastases (CRLM) between 2012-2018. We reviewed patient, disease, and tumor characteristics and measured local, intrahepatic, and extrahepatic recurrence (EHR) rates. We also calculated median overall survival (OS) and disease-free survival (DFS). Results: Ten patients identified had five or more (range, 5-18) tumors ablated with or without combined liver and bowel resection. Median age was 50, and most patients were male (70%) and Caucasian (90%). Four patients received ablation alone (5-12 lesions), while six had combined resection and ablation (5-18 lesions). Ablation was performed laparoscopically in six patients, and four had ablations without resection. All patients received pre-and post-operative chemotherapy. A median of 7 tumors were ablated per patient. Median follow-up was 2.3 years. Among 75 tumors ablated, ablation site recurrence (ASR) (within 1 cm of ablation site) was seen in three with a per-lesion recurrence rate of 4%. Intrahepatic recurrence (IHR) occurred in 6 (60%) patients and EHR in 1 (10%). Five patients underwent retreatment of IHR during follow-up. Median OS was 3 years and DFS was 7.1 months. At the time of last follow up, 6 patients were disease-free. Conclusions: Thermal ablation can provide acceptable DFS and OS, even with high volume metastatic colorectal cancers. Future efforts should be focused on defining selection criteria for those most likely to benefit from this aggressive approach.