Because MWA is a more recent addition to the surgeon’s armamentarium, the discussion will proceed from the perspective of the RFA literature and except for several caveats, which differentiate RF from MW energy, the assumption is made that the clinical performance of MWA is at least that of RFA. Our discussion will not include “cold” thermal ablation (cryoablation), chemical ablation (Cediranib cost percutaneous ethanol injection, acetic acid injection,

etc) electrical ablation (irreversible electroporation, IRE), or high intensity focused ultrasound (HIFU) as RFA and MWA are the Inhibitors,research,lifescience,medical most commonly utilized technologies at the present time. Radiofrequency Ablation RFA induces tumor necrosis by achieving local hyperthermia with temperatures exceeding 58°C. RFA is based on alternating current of radio frequency waves (≈500 KHz) that are transmitted via a probe into tissue to cause ionic agitation, which generates frictional Inhibitors,research,lifescience,medical heat that extends into adjacent tissue by conduction. Eventually, hyperthermia leads to cell destruction as a result of coagulative Inhibitors,research,lifescience,medical necrosis (14). RFA can be performed under US, CT, or MRI guidance. This can be achieved by percutaneous, laparoscopic, or open surgical approaches, depending on operator preference, tumor anatomy, and extent of disease. However, multiple studies (15-18) have shown that the open surgical approach is superior to percutaneous approach Inhibitors,research,lifescience,medical in terms of minimizing local recurrence

rates. Better exposure of the liver, ability to visually

inspect and palpate surface liver lesions, and ability to use intra-operative ultrasound with its associated high sensitivity to detect additional lesions may explain the superior results of surgical approach (19-21). Limitations of RFA Tumor number and tumor size are important Inhibitors,research,lifescience,medical determinants of local recurrence rates or treatment failure after RFA. Patients with solitary CRHM have been shown to have better survival and lower recurrence rates compared to those with multiple CRHM (22,23). Similarly, patients with tumors of size less than or equal to 3 cm have better recurrence free survival following ablation (16,24,25). The optimal negative margin Bumetanide size or ablation zone extension beyond the tumor border for RFA of CRHM has not yet been standardized. Currently, ablating to a negative margin of 0.5 – 1 cm has been recommended (15,20). On the other hand, one study (26) has showed that the rate of local tumor progression was independent of the size of the post-ablation margin, and a meta-analysis (21), suggested that 1 cm intentional margin was not a significant factor on multivariate analysis, for local recurrence However, there is no disagreement that complete eradiation of tumor cells in the target lesion(s) is primary goal of any attempt at ablation. Reported rates of local recurrence from RFA for CRHM range widely, from 2% to 40% (10,20,27).