Generally, surgical resection is a more radical treatment approach than RFA. However, due to the limitations of the liver condition and function, postoperative complications also need to be taken into account. RFA surgery is a relatively safe treatment approach, but the stability and thoroughness of RFA for treating liver cancer are difficult to determine[10, 11]. Although the evaluation of effectiveness between the two approaches is still under debate, in Western countries, especially in the United States, the treatment guidelines for liver cancer consistently recommend surgical resection for early liver cancer if the liver function allows it and if there is not high vein pressure[12]. However, the guidelines also mention that due to the nearly 3% mortality rate after liver resection surgery, the use of other therapies to treat small liver tumors may be appropriate, of which ablation treatment is preferred. At present, the relevant mature ablation treatment method is RFA. There have been many studies on the effectiveness and reliability of the treatment of liver cancer using RFA and surgical resection. Although a unified opinion has not yet been reached, we believe that the effect of RFA depends on the maximum diameter of the tumor. Current studies mostly define the gold standard for RFA to be smaller than 2.3-3 cm. For a single tumor with a diameter smaller than 3 cm, RFA can achieve similar results to resection, and the safety of the patient is ensured[13-15]. However, for a tumor with a diameter in excess of 5 cm, although some reports claim that three-dimensional RFA can achieve similar results to resection, at present, most reports in the literature indicate the use of resection instead of RFA[4]. However, the focus of the current debate is on a single liver tumor that is 3-5 cm in diameter, and for these tumors, the treatment effectiveness of RFA and resection remain to be further investigated. Our study was conducted to promote an in-depth discussion of this subject.
Regarding tumor characteristics, there were more cases with the tumor located in the center of liver in the RFA group than in the resection group, mainly due jointly to preoperative CT evaluation and intra-operative examination of tumor features and liver cirrhosis: when the tumor is located in the periphery of the liver, surgical resection is relatively easy, especially for a tumor in the left lateral lobe; in contrast, RFA ablation is prone to injuring other surrounding tissues, such as the stomach or colon[6]. In addition, the implementation of RFA for peripheral small liver tumors is more prone to cause tumor rupture and result in metastasis[4, 16]. When the tumor is located in the center of the liver, however, especially at the junction of the donor in segments V, VI, VII, and VIII of the right side of the liver, liver resection will result in the loss of a large amount of normal liver tissue, leaving too small a volume in the residual liver[16]. Because most of the liver is often cirrhotic in these patients, postoperative liver function cannot satisfy organ metabolism, leading to liver function failure or even death. Moreover, when the tumor is close to large blood vessels, the result of using RFA is poor and often leaves behind part of the tumor tissue. Therefore, in the clinical application of RFA, we need to consider not only the diameter of the tumor but also its location, the surrounding tissue and the background liver condition to achieve better results.
Although a small incision means that RFA surgery leads to significantly less blood loss, cases requiring blood transfusion are rare because the blood loss during resection surgery is also small in our hospital. Therefore, although the blood loss was different for the two groups, there was no significant difference in the rate of blood transfusion for the two groups. Because the trauma of resection is relatively great, the surgery requires partial occlusion. The most commonly used method is semi-liver occlusion, which can prevent injury to the remaining liver due to continuous occlusion by ischemia-reperfusion. However, in our analysis and comparison, although the intra-operative time was short, the blood loss during surgery was small, and the postoperative hospital stay was short, there was still a significant difference between the total treatment expense in the RFA group and the resection group, mainly because the domestic hospitals usually use imported RFA needles. The RFA needle costs nearly 10,000 RMB Yuan, which accounts for most of the treatment cost of the RFA treatment, whereas the overall expense of surgical resection is low. Hence, there was no difference in the total treatment expense between the resection group and the RFA group. Through the observation of postoperative complications, we found that although the occurrence rate of postoperative complications and the occurrence rate of serious complications were both higher in patients in the resection group than in the RFA group, this difference was not statistically significant. One possible reason could be that our sample size is not large enough, and all our cases of RFA underwent abdominal surgery. Therefore, in comparison with other statistical analyses, our data are more objective and accurate. However, this topic still needs a multi-center randomized comparison and a large sample to further explore the occurrence of postoperative complications for the two methods.
Our analysis indicates that the postoperative 1-, 3-, and 5-year survival rates are similar for the RFA group and the resection group, which is similar to the results of the 18th national statistical analysis of Japan; they conducted a statistical analysis of over 10,000 cases of liver cancer with level A liver function. They found that RFA not only achieves a similar result to resection for liver tumors smaller than 2 cm but also for liver tumors that are 2-5 cm in diameter; their observations extended up to 10 years[17]. Meanwhile, our univariate and multivariate analyses of the factors contributing to the overall survival and tumor-free survival rates indicated that resection or RFA did not contribute to overall survival or tumor-free survival. Our study again corroborates this point.
There are still some limitations of this study: although the sample size in this study is relatively large, all the patients were from a single center, and the study of patients from multiple centers is more persuasive. In addition, this was a retrospective analysis. We retrospectively collected and compared the characteristics of two groups of patients. Because our selection of resection and RFA before and during the surgery is mainly determined according to the tumor position found on pre-operative CT and during the surgery, the method could not be assigned randomly. Therefore, a multi-center randomized comparative study with a large sample will be more persuasive, and this goal is also the direction of our future work.
Because there are fewer complications after RFA surgery, which has better intra-operative and post-operative performance and a post-operative survival rate comparable to that of resection surgery, abdominal RFA can be considered for wide application to single tumors with diameters of 3-5 cm, especially for central cases.