Available percutaneous ablative procedures for HCC include:

Radiofrequency ablation (RFA) – is a minimally invasive procedure that uses electrical energy and heat to destroy cancer cells. A needle is inserted through the skin into the cancer tissue and the heat produces coagulation necrosis and subsequent cell death. While RFA is a simple, repeatable, standardized, lower risk procedure, it is limited by only having a small area of effectiveness since electrical impedance develops as the tissue boils and becomes charred. This insulates the tissue from the electrical signal and results in an effective area of only few millimeters. The effectiveness of RFA is also reduced when used near large blood vessels since this results in a heat sink effect where the heat is dissipated by the blood flowing through these vessels. Besides tumor location, other factors which impact the effectiveness of RFA include the size and number of tumors and the need for a large tumor-free margin.
Microwave ablation (MWA) – uses high frequency microwave energy to heat and kill cancer cells. A thin probe containing an antenna which emits microwaves is into the tumor. The probe produces intense heat that destroys tumor tissue via coagulation necrosis, often within 10 minutes. MWA has a number of advantages over RFA including faster heating over a larger area, shorter procedure time, no need for a grounding pad, resistance to the heat sink effect, and less pain. MWA has replaced RFA at many institutions due to the lack of a heat sink effect, as well as its speed and ease compared with RFA.

A recent systematic literature review and meta-analysis compared the efficacy and safety of MWA and radiofrequency ablation in the treatment of hepatocellular carcinoma.3  MWA was reported to have a lower rate of local tumor progression than RFA. There was no significant difference in the complete ablation rate between MWA and RFA for randomized controlled trials. No difference was seen in 1-year, 3-year, or 5-year overall survival rate or major complications between MWA and RFA for either randomized controlled trials or cohort studies. A separate systematic literature review and meta-analysis focused on the efficacy and safety of single- and multiple antenna MWA for the treatment of HCC and liver metastases.4 The overall complete ablation rate for MWA was 94.4%. The complete ablation rate for tumors >2 cm was 98.3% for multiple-antenna MWA versus 79.2% for single-antenna MWA. Multiple-antenna MWA group and single-antenna MWA group had similar local tumor progression-free (LTPF) rates with multiple antenna MWA reported to have a LTPF rate of 85.9%. Multiple- and single-antenna MWA had similar rates of complications and efficacy relative to one- and three-year overall survival.

Cryoablation –  Cryoablation causes rapid cooling of the target tissue, resulting in intracellular ice crystal formation that destroys organelle and cell membranes and induces membrane pore formation that disrupts the electrochemical gradient. Cellular tonicity is also disturbed, causing lethal transmembrane fluid shifts. If these changes do not cause immediate cell death, they often initiate apoptosis. The ability to visualize ice ball formation, the edge of which marks the 0°C isotherm, in cryoablation on several imaging modalities is a particular benefit.

While RFA and MWA have demonstrated effectiveness in the treatment of liver tumors, they are not ideal for treating lesions  near critical structures.5,6 Cryoablation is typically preferable for the treatment of tumors located near important anatomical structures due to the reduced risk of tissue damage beyond the area of tumor ablation necrosis.7 Additionally, the use of cryoablation avoid the heat sink effect observed with RFA and MWA which can also lead to ineffective ablation of perivascular tumors.

A recent systematic review and meta-analysis reported that cryoablation has a similar rate of local tumor progress and overall survival compared to RFA, but had a higher rate of complications, especially thrombocytopenia and renal impairment following microwave ablation.8

Irreversible electroporation (IRE) therapy – IRE is a nonthermal ablation technique that induces cell death by disrupting the electric potential gradient across cell membranes, leading to the formation of permanent nanopores through the plasma membrane, altering cellular transport and ultimately cell homeostasis.9 The procedure involves the delivery of a series of high voltage direct current electrical pulses between two electrodes placed within a target area surrounding the tumor. Since IRE is a nonthermal treatment, it has the advantage over thermal ablative treatments since the treatment zone can cross large blood vessels and bile ducts without damaging these vital structures.

Outcomes associated with the use of IRE for patients with HCC who were not candidates for resection or thermal ablative therapies because of a high risk of major complications have been reported.10 Complete ablation was achieved for 92% of tumors with a local tumor progression of 20% which were completely ablated. Only 5% of patients experience major complications with no complications related to bile duct injury.