Radiofrequency Ablation of Colorectal Liver Metastases: Where Are We Really Going?
Authors: Graeme J. Poston
Journal: Journal of Clinical Oncology (2005)

The use of radiofrequency ablation (RFA) for the treatment of colorectal liver metastases has been approved by the US Food and Drug Administration for several years, and this therapy is now being adopted worldwide. However, US Food and Drug Administration approval of medical devices and techniques relates only to safety and feasibility, and does not relate to proven clinical benefit, which is necessary for approval of new drugs and their indications. RFA appears to be beneficial in the treatment of primary hepatocellular carcinoma, where its use has received the tentative support of the UK National Institute for Clinical Excellence. There is also growing interest in its use at other sites of colorectal cancer, including the treatment of lung metastases. RFA is being used increasingly as an adjunct to surgical resection of colorectal liver metastases, as an alternative to resection if the disease is deemed inoperable at laparotomy, with some authors even arguing equivalence of outcome when compared with surgical resection of low-volume liver disease. With the evolution of more powerful generators (commercial generators can now produce 300 W of energy, sufficient to destroy a sphere of tissue of 6 to 7 cm diameter in 10 to 20 minutes), and better results achieved by hepatic inflow occlusion, the responses of liver tumors to RFA destruction are now highly predictable and reproducible. The report by Berber et al in this issue of Journal of Clinical Oncology, therefore, is both timely and welcome. This study reports one of the largest prospective series of patients with colorectal liver metastases treated with RFA. The authors present an honest and frank assessment of the use of this technique, with the first large-scale study addressing predictive factors for patients undergoing this treatment. By 2003, 1 year after completion of the study period, the widely accepted definition of surgical resectability of colorectal liver metastases was essentially any number of metastases (unior bilobar) as long as no more than 70% of liver (five to six of the eight liver segments) needed to be removed. One might therefore be concerned about the definition of resectability of liver metastases employed at this particular center, in view of the fact that only 44 patients underwent liver resection during the 5-year study period, whereas 328 patients underwent laparoscopic RFA. However, the 135 consecutive patients recruited to the study already fall into a poorer prognostic group, including recurrence after previous liver resection, disease progression while receiving chemotherapy, or presence of extrahepatic disease. The authors are to be congratulated on attempting to perform laparoscopic RFA, rather than percutaneous RFA in patients after previous liver resection, bearing in mind the difficult dissection frequently encountered by experienced liver surgeons at open surgery in these patients. Berber et al have shown that predictive factors for better survival after RFA include a preprocedure serum carcinoembryonic antigen of less than 200 ng/mL, dominant lesion size of less than 3 cm diameter, and three or fewer tumors. Although one might wonder why patients who fell into the latter two groups were not considered for resectional surgery rather than entry to the study, these results are similar prognostic factors for outcome after hepatectomy and cryosurgery for the same condition. Taken together, these results bear out the currently accepted rule of fives (five or fewer tumors, smaller than 5 cm diameter) when selecting patients with colorectal liver metastases for RFA treatment by whatever route of access: percutaneous, laparoscopic, or open surgery. There are concerns about taking the results of the study by Berber et al at face value for two reasons. First, at the time of RFA, 40 of their patients (30%) had extrahepatic disease, which apparently went untreated. In this scenario, one questions the purpose of the RFA regarding whether the treatment intention was to improve the liver computed JOURNAL OF CLINICAL ONCOLOGY E D I T O R I A L VOLUME 23 NUMBER 7 MARCH 1 2005