Role of thermal ablation in the management of colorectal liver metastasis.

With a recent randomized prospective trial revealing that thermal ablative therapy as local tumor control improved overall survival (OS) in patients with unresectable colorectal cancer liver metastases (CRLM), thermal ablation continues to remain as an important treatment option in this patient population. Our aim of this article is to review the current role of the ablative therapy in the management of CRLM patients. Main indications for thermal ablation include (I) unresectable liver lesions; (II) in combination with hepatectomy; (III) in patients with significant medical comorbidities or poor performance status (PS); (IV) a small (<3 cm) solitary lesion, which would otherwise necessitate a major liver resection; and (V) patient preference. There are several approaches and modalities for ablative therapy, including open, percutaneous, and laparoscopic approaches, as well as radiofrequency ablation (RFA) and microwave ablation (MWA). Each approach and ablation modality have its own pros and cons. Percutaneous and laparoscopic approaches are preferred due to minimally invasive nature, yet laparoscopic approach has more benefits from thorough intraoperative ultrasound (US) exam as well as complete peritoneal staging with laparoscopy. Similarly, whereas high local tumor failure rate has been a major concern with RFA, MWA or microwave thermosphere ablation (MTA) have demonstrated significantly improved local tumor control due to homogenous tissue heating, ability to reach higher tissue temperatures, and less susceptible to the "heat-sink" effect. Although liver resection is the standard of care for CRLM, there have been some retrospective studies demonstrating similar oncological outcome between ablative therapy and surgical resection in very selected populations with small (<3 cm) solitary CRLM. Lastly, ablative therapy and liver resection should not be mutually exclusive, especially in the management of bilobar liver metastases. Concomitant ablative therapy with hepatectomy may spare the patients from having two-stage hepatectomy with less morbidity. The role of the thermal ablation will continue to evolve in patients with resectable and ablatable lesions owing to newly emerging technology, in addition to new systemic treatment options, including immunotherapy for metastatic colorectal cancer (CRC).