Microwave Ablation of Liver Metastases Guided by Contrast-Enhanced Ultrasound: Experience with 125 Metastases in 39 Patients

Abstract

The aim of our study was to evaluate the efficacy of microwave (MW) ablation of liver metastases guided by B-mode ultrasound (US) and contrast-enhanced US (CEUS). 39 patients (17 women and 22 men) with a total of 125 liver metastases were treated with percutaneous or intraoperative CEUS-guided MW ablation. The primary tumor was colorectal cancer (n = 31), breast cancer (n = 6), carcinoid tumor (n = 1), and gastrointestinal stromal tumor (GIST) (n = 1). The median number of metastases ablated in the 45 treatment sessions was 2 (range 1 - 11). The median size (maximum diameter) of the 125 metastases was 1.5 cm (range, 0.6 - 4.0 cm). Nineteen (15 %) of the 125 metastases were bigger than 2 cm. Metastases smaller than 2 cm were treated with a single needle, metastases bigger than 2 cm were treated with 2 or 3 parallel needles. The 45 MW ablation sessions were performed percutaneously (n = 30), during laparotomy (n = 3), or during laparotomy combined with liver resection (n = 12). The 39 patients were followed up for at least 4 months with a median duration of 11 months (range, 4 - 20 months). The technical success rate was 100 %. The clinical effectiveness was 100 % with complete coverage of the metastasis by the avascular coagulation zone evaluated on immediate post-ablation CEUS. Local tumor progression (local recurrence) was seen in 12 (9.6 %) of the 125 treated metastases, and affected 10 (26 %) of the 39 patients. One major complication was observed in the form of a liver abscess that easily resolved after percutaneous drainage. Four minor complications were observed: Three cases of pain located at the puncture site and one case of ascites. CEUS was valuable in all phases of ablation including pre-ablation staging and procedure planning, placement of MW needles in the tumor, immediate post-ablation control of coagulation size, and finally in the long term follow-up regime. CEUS-guided MW ablation of liver metastases is an efficient and safe ablation technique with several advantages compared to other ablation modalities.