Thermal Ablation for Colorectal Liver Metastases

Hepatic resection in combination with systemic chemotherapy is a standard treatment modality for colorectal liver metastases (CRLM). Recently, thermal ablation, including microwave coagulation therapy (MCT) and radiofrequency ablation (RFA), has been utilized in the treatment of unresectable and partially resectable CRLM. A review of the English language literature and a summary of our experiences in applying thermal ablation in the treatment of CRLM are described here. RFA is used worldwide, and MCT is primarily utilized in eastern countries. In using percutaneous and laparoscopic/open surgical RFA, local recurrence rates were16% and 4% for tumors < 3 cm, 26% and 22% for tumors between 3-5 cm, and 60% and 50% for tumors > 5 cm. In a large series of treatments which utilized RFA for liver tumors, the mortality and morbidity rates were only 0.3 and 7.2%, respectively. The incidence of tumor seeding after the use of RFA for the treatment of CRLM is as high as 1.4%. Cumulative 5-year survival rates were 29%-36% using MCT and 14%-35% using RFA for unresectable CRLM. Long-term survival data for resectable CRLM are unclear. In our experience, local recurrence rates were undetectable in following the treatment of 30 cases of CRLM (average tumor diameter : 1.7 cm, average observation period : 26 months) which were treated with surgical RFA combined with hepatic resection after efficacious systemic chemotherapy. In Conclusion : 1) thermal ablation can be applied to unresectable CRLM without perivascular invasion, and for tumors < 3 cm with a percutaneous or surgical approach, and for tumors < 5 cm with a surgical approach ; 2) RFA after effective chemotherapy can provide an extremely high local control rate ; and 3) the application of thermal ablation for resectable CRLM is still controversial due to the lack of sufficient evidence obtained from a randomized trial.