Liver or Hepatic Metastases are cancers that have originated in another organ and have spread to the liver. The most common source or primary is colon cancer and most of the published studies on aggressive or active treatment of liver mets are cases that started in the colon. Liver mets can also develop from other cancers such as breast, lung, prostate, melanoma and kidney cancer

liver mets review from E Medicine
symposium on hepatic metastases
up to date on colon metastatic to the liver

see the other sections on treatment and survival statistics
Incidence
   •    Liver metastases are most frequently seen in patients with colorectal cancer (CRC; nearly 15% of patients presenting and an additional 60% developing subsequent spread); they are less common in patients with breast cancer (4% of initial failures), lung cancer (15%), and melanoma (24%).
Etiology
   •    The liver has a rich blood supply from both the hepatic artery and the portal vein; metastases can reach the liver from any organ, but the direct passage of blood from the gastrointestinal tract to the liver via the portal circulation plays a critical role in explaining the high rate of liver metastases from these sites.

Detection

   •    Contrast computed tomography (CT) and magnetic resonance imaging (MRI) can detect approximately two-thirds of liver metastases.
   •    CT angiography, CT portography, and intraoperative ultrasound seem to have increased sensitivity as compared with standard techniques.
   •    Positron emission tomography (PET) is more useful to detect extrahepatic disease.
   •    Of laboratory tests, carcinoembryonic antigen (CEA) can be useful for patients with metastatic CRC to the liver.
Treatment

Hepatic Resection

   •    There is general agreement that surgical resection is the treatment of choice for patients with one to three metastases from CRC, producing a 5-year survival of about 30%.
   •    Significant advances in surgical technique include the ability to perform metastasectomies (rather than formal lobectomies) and total vascular exclusion.
   •    The liver is the chief site of relapse after hepatic resection (50% of all patients).
   •    Prognostic variables that influence survival after hepatic resection include the presence of extrahepatic disease, the stage of the primary colon cancer, the time interval between primary and the development of hepatic metastases, and the number of metastases and positive margins.
   •    The use of adjuvant hepatic artery infusion (HAI) after liver resection has produced positive results in two American trials. There is a clear decrease in hepatic recurrence with adjuvant HAI.
Systemic Chemotherapy
   •    The objective response rate with intravenous chemotherapy is improving, with response rates of 40% to 50% among patients with breast cancer, gastric cancer, and now even colon cancer.
Hepatic Artery Infusion
   •    Eight randomized trials demonstrate a higher response rate for HAI than for systemic infusion (42% to 64% vs. 0 to 38%, respectively). Survival advantage is difficult to interpret: two large U.S. studies allowed a crossover from systemic therapy to HAI after tumor failure. New CALGB study without crossover showed a survival advantage. The chief toxicity of HAI is biliary enzyme elevations in 40% and biliary sclerosis in 5% to 35% of patients.
Hepatic Artery Embolization
   •    Embolization could play a role in highly vascular tumors (neuroendocrine tumors and hepatocellular carcinoma, HCC).
   •    Embolization agents include Gelfoam, lipiodol, and degradable starch microspheres.
   •    Embolization is rarely useful for patients with metastatic CRC.
   •    Chemoembolization involves the local entrapment of drug in the embolization agent in an attempt to provide a prolonged exposure of the tumor to drug locally, with less systemic exposure.
Ablative Techniques
   •    Cryosurgery involves destruction of tissue using a freezing probe.
   •    Limitations include the difficulty of controlling freezing and the typical requirement for laparotomy.
   •    Radiofrequency ablation involves destruction by frictional heat and can be used percutaneously but is rarely good for lesions larger than 3 cm.
Absolute Ethanol Injection
   •    Ethanol is injected into the tumor under ultrasound guidance and could be of use for small HCCs.
Radiation
   •    Whole-liver external-beam irradiation therapy alone is limited by the occurrence of radiation hepatitis to about 30 Gy in 15 fractions.
   •    Parts of the liver can be treated to far higher doses using yttrium-90 (90Y) microspheres, interstitial brachytherapy, and external-beam irradiation therapy guided by three-dimensional treatment planning.