**9. Conclusions**

Optimal treatment strategies for CRLM patients should be made by a multidisciplinary team as part of a tumor board, for establishing diagnostic and treatment strategies [1]. Surgery of CRLM will likely provide the best long-term outcomes and the strategy should focus on complete resection. Although, the majority of patients with CRLM are ineligible for surgery and many surgical cases will experience widespread recurrence. Thermal ablation methods like focused ultrasound are generally only recommended for unresectable CRLM and oligometastatic disease, with at least one system under ultrasound guidance having the CE-mark for CRLM [1, 2]. Due to expected increasing CRLM incidence and high surgical ineligibility, non-invasive technologies like MRgHIFU systems have great potential for clinical translation as an ablative interventional radiology procedure.

Guidelines for FUS pilot studies suggest performing MRgHIFU ablation in CRLM patients prior to the surgical operation, then surgically removing the ablated tumor, and assessing the effectiveness with pathology [2]. Randomized control trials have been suggested to be performed on CRLM patients that are not candidates for surgical resection or RF ablation, and to compare TACE and MRgHIFU to a control group receiving only TACE [2]. In a randomized controlled trial, USgFUS for primary liver tumors in combination with TACE has shown improved treatment over TACE alone, increasing survival times, giving higher remission rates, lower recurrence rates, lower rates of post-operative metastases, and less instances of hemorrhaging in the digestive tract [199, 200].

MRgHIFU has been established in proof-of-concept studies for HCC, limited to the left liver lobe or section not covered by the ribs, requiring intermittent ablation due to respiration, and has not been reported in randomized controlled trials for primary or secondary liver tumors [170, 187–189, 196, 197, 201]. The FUS field has gained much interest in recent years and MRgHIFU ablation of primary and secondary liver tumors appears likely to begin early phase trials in the near future. Previous focused ultrasound studies have developed methods to address many technical complications such as respiratory motion and suppressing prefocal interactions; with focusing through the ribs being one of the major technical difficulties. Long treatment times are another complication and should improve with automated feedback control and faster acquisition times.

*Magnetic Resonance-Guided Focused Ultrasound in the Treatment of Colorectal Cancer Liver… DOI: http://dx.doi.org/10.5772/intechopen.105906*
