**2.3.1 Radiofrequency ablation (RFA)**

RFA is a thermo-ablative technique, which works by using a high-frequency alternating current applied via electrodes placed within the tissue to induce temperatures changes and generate areas of coagulative necrosis and tissue desiccation. RFA has been increasingly used to treat small primary or recurrent HCC (<5cm) in patients with poor liver reserve (Lau & Lai, 2009). High complete ablation rate (over 90%) and long-term survival comparable to those achieved by hepatectomy have been reported by cohort studies on RFA to treat recurrent HCC after partial hepatectomy. The reported 3-year survival rate averaged above 60% and the 5-year overall survival rate ranged from 18%-51.6% (Camma et al., 2005; Chen et al., 2006; Choi et al., 2007; Lu et al., 2005; Poon et al., 2002; Tateishi et al., 2005; Taura K et al., 2006; Yang et al., 2006).

Besides the good results it achieves, RFA also has a few advantages over the repeat hepatectomy. First of all, it can be used in patients with poor liver function who might not be able to tolerate a repeat hepatectomy. Being a minimally invasive technique, RFA can be applied percutaneously in suitable patients and avoid the risk associated with general anesthesia and laparotomy (Figure. 2). Furthermore, RFA can be applied repeatedly for repeated treatment of recurrence. It is particularly important since in the background of liver cirrhosis, HCC tends to recur repeatedly and repeated treatment may be necessary. Hence, treatment with minimal damage to the non-tumoral hepatic parenchyma may be more preferable.

done by surgeons who are highly experienced in both laparoscopic and open hepatic

Tumor ablation is defined as the direct application of chemical or thermal therapies to a tumor to achieve eradication or substantial tumor destruction. Although repeat hepatectomy is the most effective treatment for recurrent HCC, impaired liver function and the presence of multicentric tumours often precludes repeat hepatectomy in more than 80% of patients with recurrent HCC (Arii, et al. 1998; Kakazu et al., 1993; Lu et al., 2005; Minagawa et al., 2003; Poon et al., 1999; Shimada et al., 1996; Suenaga et al., 1993). Local ablative therapies have been increasingly used to treat recurrent HCC. They are particularly suitable for treatment of recurrent HCC as recurrence can usually be detected at an early

stage on the surveillance imaging after hepatectomy while the nodules are still small.

Radiofrequency ablation (RFA), microwave coagulation therapy (MCT) and percutaneous ethanol injection (PEI) are the three most commonly used local ablative treatment modalities for treatment of small primary HCC. Reports on the use of PEI in treating HCC recurrence are scarce. Both RFA and MCT can be applied percutaneously, laparoscopically, or at open surgery. From the experience in treating primary HCC, RFA and MCT are able to destroy bigger tumor up to 6cm or 7cm in diameter and require fewer treatment sessions than PEI and are therefore gaining attention as a valuable treatment options for ablating recurrent HCC (Goldberg & Gazelle, 2001; Ikeda et al., 2001; Livraghi et al., 1999; Lu et al., 2001; Seki et al., 1999). Currently, most of the currently available results on local ablative therapy for

RFA is a thermo-ablative technique, which works by using a high-frequency alternating current applied via electrodes placed within the tissue to induce temperatures changes and generate areas of coagulative necrosis and tissue desiccation. RFA has been increasingly used to treat small primary or recurrent HCC (<5cm) in patients with poor liver reserve (Lau & Lai, 2009). High complete ablation rate (over 90%) and long-term survival comparable to those achieved by hepatectomy have been reported by cohort studies on RFA to treat recurrent HCC after partial hepatectomy. The reported 3-year survival rate averaged above 60% and the 5-year overall survival rate ranged from 18%-51.6% (Camma et al., 2005; Chen et al., 2006; Choi et al., 2007; Lu et al., 2005; Poon et al., 2002; Tateishi et al., 2005; Taura

Besides the good results it achieves, RFA also has a few advantages over the repeat hepatectomy. First of all, it can be used in patients with poor liver function who might not be able to tolerate a repeat hepatectomy. Being a minimally invasive technique, RFA can be applied percutaneously in suitable patients and avoid the risk associated with general anesthesia and laparotomy (Figure. 2). Furthermore, RFA can be applied repeatedly for repeated treatment of recurrence. It is particularly important since in the background of liver cirrhosis, HCC tends to recur repeatedly and repeated treatment may be necessary. Hence, treatment with minimal damage to the non-tumoral hepatic parenchyma may be

surgeries.

**2.3 Local ablation therapies** 

recurrent HCC were using RFA.

K et al., 2006; Yang et al., 2006).

more preferable.

**2.3.1 Radiofrequency ablation (RFA)** 

Fig. 2. CT image of a CT-guided percutaneous RFA of a segment VIII recurrent HCC which was performed under local anaesthesia.

Liang et al compared the long-term survival outcomes of percutaneous RFA and repeat partial hepatectomy for recurrent HCC (Liang et al., 2009). They found that there was no significant difference in the overall survival of patients with recurrent HCC treated by repeat hepatectomy or RFA while RFA had the advantage over hepatectomy in being less invasive and causing fewer treatment-related morbidities. The authors attempted to make the baseline demographics in two arms comparable by using the same selection criteria to identify patients received repeat hepatectomy and percutaneous RFA in order to minimize the selection bias. The criteria included fewer than three recurrent tumours with the largest one less than 5cm, no radiological evidence of venous invasion, no extrahepatic metastases, no severe liver dysfunction (Child-Pugh class C), no significant coagulopathy, and no history of encephalopathy, refractory ascites or variceal bleeding.

Of note, as in repeat hepatectomy, the benefit of RFA was more promising for patients with a longer disease-free interval from hepatectomy (Liang et al., 2009; Yang et al., 2006). Yang et al studied 41 patients with 76 recurrent HCC who received percutaneous RFA after hepatectomy. Early and late recurrences were defined as recurrence that occurred within 1 year and after 1 year respectively (Yang et al., 2006). The late-recurrence group had a significantly longer overall survival than the early-recurrence group (mean overall survival 42.9 months *versus* 16.4 months).

Needle tract dissemination is one of the major complications of great concern in percutaneous ablations. (Figure. 3) In a phase II study assessing the treatment-related complications and response rate of RFA in 32 patients by Llovet et al reported that the incidence of needle tract dissemination after radiofrequency ablation was as high as 12.5% (Llovet et al., 2001).

Fig. 3. Patient with metastasis at the needle tract (a) after underwent CT-guided RFA for HCC (b).
