AIM: To evaluate the therapeutic efficacy of radiofrequency ablation (RFA) for resectable colorectal liver metastases (CRLM) compared with that of resection.

METHODS: Between June 2004 and June 2009, we retrospectively analyzed 29 patients with resectable CRLMs; 17 patients underwent RFA, and 12 underwent hepatic resection. All of the patients were informed about the treatment modalities and were allowed to choose either of them. RFA including an intraoperative approach was performed by a radiologist; otherwise, hepatic resection was performed by a surgeon. Comparative analysis of the two groups was performed, including comparisons of gender, age, and clinical outcomes, such as primary tumor stage and survival rates.

RESULTS: The mean tumor size was significantly larger in the resection group (3.59 cm vs 2.02 cm, P < 0.01), and the 5-year overall survival (OS) rate for all patients was 44.7%. There was no difference in the 5-year OS rates between the RFA and resection groups (37.8% vs 66.7%). Univariate analysis indicated significantly lower 5-year OS rates for patients with a tumor size > 3 cm. The 5-year disease-free survival (DFS) rates were 17.6% and 22.2% in the RFA and resection groups, respectively (P = 0.119). Univariate analysis revealed that in cases of male gender, age > 65 years, T stage < IV, absence of lymphatic metastasis, and tumor size > 3 cm, RFA resulted in significantly inferior 5-year DFS rates compared with surgical resection.

CONCLUSION: Surgical resection revealed superior outcomes in the treatment of resectable CRLMs, particularly in cases with a hepatic tumor size > 3 cm.

A 2005 annual report of cancer incidence indicated that colorectal cancer (CRC) is the third most common malignancy worldwide and the second most common (12.5%) in Korea, following gastric cancer. The 5-year survival rate of CRC is reportedly 61%[1,2], and hepatic metastasis develops in approximately 40%-50% of patients with CRC; approximately 50% of diagnosed patients present the synchronous type[3-5]. Although surgical resection is the most effective current treatment for resectable colorectal cancer liver metastases (CRLMs)[6,7], only 10%-15% of such cases are suitable for the procedure[8,9]. Several alternative treatment modalities for unresectable CRLMs have been developed, of which radiofrequency ablation (RFA) is widely accepted as an effective alternative local treatment modality[10].

Surgical hepatic resection is the treatment of choice for resectable CRLMs. Although RFA is an alternative to resection in hepatocellular carcinoma[11,12], there is little information regarding indications for RFA in resectable CRLMs. RFA is performed within a limited number of clinical settings for resectable CRLMs[13,14]. The purpose of the present study was to compare the therapeutic efficacies of RFA and hepatic resection for resectable CRLMs within a single institution.

In this study, we compared the treatment outcomes of 12 patients who underwent hepatic resection with 17 who underwent RFA for synchronous or metachronous resectable CRLMs between June 2004 and June 2009 at the Department of Surgery, Pusan National University Hospital (Busan, South Korea). The inclusion criteria for this study were as follows: (1) no signs of preoperative extrahepatic metastases; (2) tumor size < 5 cm; and (3) a single metastatic tumor. The exclusion criteria were as follows: (1) simultaneous performance of resection and RFA; (2) resection of hepatic recurrence after RFA; (3) lymph node metastases identified during or after resection; and (4) associated multiple hepatic metastases. The selection of patients for each treatment modality was fully based on the patient’s decision.

Surgical resection is the treatment of choice for resectable CRLMs, whereas RFA has been used for unresectable CRLMs as an alternative treatment to improve patient survival[13,14]. While some series have reported RFA equivalent to resection, others have shown RFA to be inferior to resection based on overall survival[15-17]. However, the efficacy of RFA for resectable CRLMs remains controversial. Reuter et al[18] reported superior DFS rates in patients with resectable CRLMs following surgical resection than following RFA. By contrast, Mulier et al[19] reported no significant difference in OS between RFA and surgical resection for local control of CRLMs. Furthermore, in a recent study, Kanas et al[20] reported a 5-year OS rate of 30%-40% in patients with resectable CRLMs. Moreover, they observed that the survival rate in the resection group was favorable and reported that statistical significance could be expected using a larger patient population, even in the actual 5-year OS rate in the RFA group and in the nonactual survival in the resection group. Our 5-year OS rates were 66.7% in the resection group and 37.8% in the RFA group (actuarial 5-year survival rates), which is comparable to those reported in other published studies. In patients with hepatic tumors < 3 cm, the 5-year OS rate was 80.0% in the RFA group and 49.5% in the resection group (P = 0.46). In patients with a hepatic tumor size > 3 cm, the 5-year OS rates were 0% in the RFA group and 57.1% in the resection group (P = 0.005). In addition, the DFS rate in the resection group was superior to that in the RFA group.

To date, there exist some controversies regarding the contribution of clinicopathological factors to survival following surgery for resectable CRLMs[21]. Surgical resection in CRLM is considered the treatment of choice for local tumor control rather than systemic therapy. RFA, which has the advantages of minimal invasiveness and sparing the liver parenchyma, might be favorable for the local control of CRLMs, which requires adjuvant chemotherapy as well[19]. However, less definitive evidence exists regarding the risk of intrahepatic or hematogenous metastases after RFA for patients with CRLMs. Fourteen patients who underwent RFA in our study experienced recurrences of multiple liver metastases and peritoneal carcinomatosis, and two patients developed metastases in the lung and spleen. The local recurrence rates after RFA are reportedly 2%-40%[22-25], and Abitabile et al[26] reported that local recurrence rates reached 8.8% overall and 1.6% for CRLMs < 3 cm in diameter. In the present study, one patient developed tumor recurrence following RFA and was excluded; the patient was followed up for 37 mo without recurrence after consecutive hepatic resection.

The statistical analysis in the present study identified the following risk factors for poor DFS in the RFA group compared with the resection group: male gender, age > 65 years, lower T stage, colon cancer, and absence of lymph node metastasis. These findings might be the result of the omission of intensive adjuvant chemotherapy in patients with less-advanced CRC stages.

Some limitations to the present study include its retrospective design and the small number of included cases. However, to our knowledge, this is the first report regarding the actuarial 5-year survival rate after RFA, which was 37.8% in patients with resectable CRLMs. Surgical resection is believed to be superior to RFA for resectable CRLMs; nevertheless, RFA displayed some interesting advantages to justify its adoption in patients with resectable CRLMs. Although a randomized controlled study of RFA is warranted, more strict indication criteria are needed before adopting RFA as a replacement for surgical resection in resectable CRLMs.