IMAGE-GUIDED
CRYOABLATION
LIVER METASTASIS —
Overview
What are Liver Metastases?
Malignant, or cancerous, liver tumors fall into two main types: primary or secondary (metastatic). Primary tumors originate in the liver itself. Hepatocellular carcinoma (HCC) is the most common type of primary liver cancer.
In the United States, cancer in the liver is most often the result of spread, or metastasis, from cancer in other parts of the body. Cancerous cells may detach from the site of the original cancer and be transported via the bloodstream to the liver. Because one of the liver's main functions is to filter blood, these cancer cells can remain behind and colonize in the liver, growing into tumors. Common secondary liver cancers include colorectal, pancreatic, stomach, and esophageal cancers. Breast cancer, lung cancer, and melanoma often spread to the liver, as well.
The risk of the spread of cancer to the liver varies. It depends on the site of the original cancer, blood flow patterns, and the characteristics of the different cancer cells. For example, cancers of the gastrointestinal tract often spread to the liver because blood flows directly from these organs to the liver. Melanoma usually spreads through the body's blood vessels to the liver. In about 20% of cases, the cancer has already metastasized to the liver by the time the primary cancer is originally diagnosed. However, a metastatic tumor may not appear for months or even years after the primary tumor is removed.
Treatment of liver metastases depends on many factors, including the primary cancer site, the volume of liver tissue involved, whether there is one or several liver tumors, whether it has spread to other organs, and the overall medical condition of the patient. When the tumor is localized to only a few areas of the liver, it is possible that the cancer may be removed surgically. Overall, however, only 15-20% of liver tumors are able to be resected through traditional surgery.
When the cancer has spread not only to the liver but to other organs as well, systemic chemotherapy (directed at treating the entire body) is usually used. In situations when the metastasis is limited to the liver, systemic chemotherapy may be used, although other treatment methods may be more effective. Use of cryosurgery (freezing), radiofrequency ablation (RFA), or injection of toxic substances may also be used to kill tumors. When larger areas of the liver are involved, liver-directed chemotherapy (infusing chemotherapy directly into the liver), or embolization (blockage of blood flow to parts of the liver) may be used.
Percutaneous
cryoablation is a very recent addition to
the liver
cancer treatment techniques. In the past,
the relatively large size of the cryoprobes prevented
safe percutaneous placement. The introduction
of very thin 17g (1.47mm) cryoablation
needles has removed this obstacle. MRI compatible
cryoablation needles and thermal sensors are also
available, allowing cryoablative treatment for
liver cancer to be performed safely as a minimally-invasive
procedure under CT or MRI image guidance by a
physician specializing in interventional radiology.
The ability to perform the procedure percutaneously
may expand the patient population that can receive
curative as well as palliative treatment for hepatic
malignancies.
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