Ablation Therapy in Liver Cancer

Ablation therapy has been used for quite some time to treat various heart and vein disorders. Ablation therapy for atrial fibrillation is the grandfather of radiofrequency ablation therapies. In these ablations therapies, radiofrequency ablation energy (think microwave oven energy) is applied to a discrete bit of tissue which is destroyed. More recently physicians have applied ablation therapy to the treatment of cancer. The cancer type that has been treated most often and effectively by ablation therapy is cancer of the liver. This article discusses the two main types of ablation therapy used to treat liver cancer.

 

 

Liver cancer is particular amenable to ablation therapy for several reasons. In general, fewer than half of all patients with primary liver cancer (hepatocellular carcinoma) are candidates for surgery and, even in those that do qualify, the cancer often recurs in a site surrounding the removed section of liver. Therefore there are many patients that are potential candidates for endovenous ablation therapy or intraarterial ablation therapy because they are not candidates for traditional cancer resection surgery. Also primary liver tumors and metastatic tumors that seed in the liver are solid tumors and often have an extensive blood vessel supply. The rich blood vessel supply makes it a relatively easy target for a cannula to be guided through the blood vessel system to the blood vessel(s) supplying the tumor. Also, the anatomy of the liver provides allows it to be relatively resistant to either the radiofrequency or cryoablation energy—the tissue surrounding the treated tumor is only minimally affected.

 

Because of its success, ablation therapy has been extended to patients other than those with inoperable liver cancer. Some early stage liver cancers are treated with radiofrequency ablation. It is also viable option for patients that are waiting for a liver transplant. In patients that have had a liver resection and the can has returned, ablation therapy offers an organ-sparing treatment.

 

The most widely and longest used energy in ablation therapy is radiofrequency ablation. It is quite similar to the focal heating action of microwave energy. In fact, experiments with microwave energy have been performing comparing it to radiofrequency ablation. The cannula is directed through the blood vessels to the tumor (as detected by radiological studies like fluoroscopy or CT) and the energy disrupts and destroys the tumor.

 

Cryoablation is another form of ablation therapy that has been used in the treatment of liver cancer. Instead of heating the tumor to disrupt it, cryoablation actually supercools and freezes the tumor. This freezing action kills the tumor cells by ice crystallization, desiccation, and then recrystallization when the tumor thaws. This approach is similar to the cryoablation that has been used by dermatologists for warts and other skin blemishes. Unfortunately, cryoablation has not been as effective as radiofrequency ablation for liver cancer. While cryoablation can be precisely controlled and can destroy tumor cells, there have been a relatively high number or cancer recurrences after this form of ablation therapy. Therefore, cryoablation is usually reserved for patients that are not candidates for surgery.