The liver is the largest organ in the body, and has multiple functions: absorption and storage of nutrients, removal of toxic wastes from the body, production of proteins that stop bleeding.
The liver receives blood from two sources: the hepatic artery, which carries oxygen-rich blood directly from the heart, and the portal vein, which delivers nutrients from the intestines. Blood from the liver is returned to the heart via the hepatic veins. The liver has the remarkable and singular ability to regenerate – as little as 25% of a liver can regrow to its original size.
Cancer from elsewhere in the body can be deposited in the liver through a process called metastasis. This usually involves cancer cells breaking off from their original site, traveling through the blood and then being delivered to the liver, where these cancer cells settle and grow. Since the portal vein carries blood directly from the intestines to the liver, this vein is a common path for colon cancer cells to travel in the blood. As a result, most liver metastases originate from colon cancer. However, liver metastases can be from many other cancers, including gastric (stomach), pancreatic, breast, lung, kidney, and melanoma.
In the United States, liver metastases (or secondary liver cancer) are much more common than primary liver cancer (in which the cancer originates in the liver, such as hepatocellular carcinoma).
Many patients with liver metastases have no symptoms or
non-specific symptoms. If symptoms occur, they may include:
A variety of tests may be used to identify liver metastases.
These tests include blood tests, imaging studies and biopsy.
From the blood, we can measure tumore markers, such as CEA. Diagnostic imaging tests are useful to not only identify liver metastes, but also provide a highly detailed picture of where the tomor or tumors are in the liver. This very important in deciding how these tumors can be treated.
Imaging techniques commonly used to diagnose liver metastases include:
Other tests may be necessary to find out where else
in the body cancer might be. These tests include colonoscopy and laparoscopy.
When liver metastases are limited in size and number, an
operation to remove them (liver resection) is the most effective treatment for
patients with liver metastases from colorectal cancer. Chemotherapy may be
given before and/or after liver resection.
Liver surgery is a challenging procedure to perform because
of the large blood vessels connecting the liver and the nearby heart.
Operations on the liver require an experienced team of surgeons,
anesthesiologists and operating room staff. Safety of these operations can be
further improved by minimizing the amount of healthy liver removed, and, in
some cases, pre-operatively performing portal vein embolization (PVE).
Performed by interventional radiologists, PVE is a procedure in which the blood
supply to the liver is partially redirected toward the healthy portion of the
liver to stimulate its growth before the operation. Having more healthy liver
remaining after the liver resection enhances post-operative recovery.
When liver metastases cannot be removed with an operation,
then an alternative is to "ablate" or burn them, thereby destroying the tumor
cells. This ablation technique involves very precisely identifying the
tumor using ultrasound or CT, inserting a needle through the skin into the
liver tumor, then applying radiofrequency or microwave energy into the tumor
via the needle. Ablation may be performed by itself (usually by interventional
radiologists) or in combination with liver resection by liver surgeons.
Another image-guided treatment is radioembolization.
This involves insertion of a catheter into the specific blood vessel supplying
the liver tumor, then injecting specially-designed radioactive beads. This
radiation kills the liver metastases without harming other
parts of the liver and body.
Chemotherapy (or systemic therapy) can be used in a number
of situations for patients with liver metastases. When liver metastases cannot
be removed with an operation, chemotherapy becomes the most important type of
treatment. For patients whose tumors can be removed with an operation,
chemotherapy can be used before and/or after liver resection.
Chemotherapy can include both traditional "cytotoxic" drugs
such as oxaliplatin and irinotecan, as well as biologic therapies, which are
targeted against specific tumor molecules. Examples of biologic therapies
include bevacizumab (Avastin®) and cetuximab (Erbitux®).
American Cancer Society http://www.cancer.org/treatment/index
Colon Cancer Alliance http://www.ccalliance.org/
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