What is liver cancer? |

Causes and Symptoms

The
liver filters the blood supply, removing and breaking down (metabolizing) toxins and delivering them through the biliary tract to the intestines for elimination with other wastes. Because of the large volume of blood flowing through the liver (about a quarter of the body’s supply), blood-borne toxins or cancer
cells migrating from tumors elsewhere (the process called metastasis) pose a constant threat. In fact, in the United States most liver cancers are metastatic; only about 1 percent actually originate in the liver. In Southeast Asia and sub-Saharan Africa, primary liver cancer is the most common type, accounting for as much as 30 percent of all cancers.

Two major types of cancer affect the liver: those involving liver cells (hepatocellular carcinomas) and those involving the bile ducts (cholangiocarcinomas). The first is by far the more common, although tumors may contain a mixture of both, and their development is similar. Tumors may arise in one location, forming a large mass; arise in several locations, forming nodes; or spread throughout the liver in a diffuse form. Liver cancers occur in men about four to eight times more frequently than in women and in African Americans slightly more than in Caucasians, although the proportions vary widely among different regions of the world. In the United States, most cancers arise in people fifty years old or older; in other areas, people older than forty are at risk.

Primary liver cancer has so much regional and gender variation because causative agents are more or less common in different areas and men are more often exposed. A leading risk factor in the United States and Europe is
cirrhosis, a scarring of liver tissue following destruction by viruses, toxins, or interrupted blood flow. In the United States, long-term
alcohol consumption is the most common cause of cirrhosis, and men have long been more likely than women to become alcoholics. Likewise,
hemochromatosis, a hereditary disease leading to the toxic buildup of iron, is a cancer precursor and more common in men than in women. In Africa and Southeast Asia, the
hepatitis B and C viruses are leading precancer diseases because hepatitis has long been endemic in those areas, whereas in the United States it is not widespread (although the number of infected people began to rise in the 1980s).

Diet and medical therapies have also been implicated as liver carcinogens. Food toxins, especially aflatoxin from mold growing on peanuts (which are a staple in parts of Africa and Asia); oral contraceptives; anabolic steroids; and the high levels of sex hormones used in some treatments are thought to increase the likelihood of hepatobiliary tumors. Genetic factors, radiation, and occupational exposure to volatile chemicals may also play a minor role.

Although researchers generally agree about which agents are liver cancer precursors, the exact mechanism leading to tumor development is not thoroughly understood. Nevertheless, one factor may be universal. Viruses and toxins injure or destroy liver and bile duct cells; the body reacts to repair the damage with inflammation and an increased rate of new cell growth, a condition called regenerative
hyperplasia. If the toxin damage continues, triggering ever more hyperplasia, as is the case with hepatitis and alcoholic cirrhosis, formation of a tumor becomes almost inevitable.

Like lymph nodes, the liver collects migrating cancer cells, so the cancers that physicians detect there often are metastases from cancers arising elsewhere in the body. In fact, liver involvement may be found before the primary cancer has been recognized. Colorectal cancer is especially given to metastasizing to the liver, since the digestive tract’s blood supply is directly linked to the liver through the portal vein; similarly, lung and breast cancer may spread to the liver. Such metastases indicate advanced cancers that do not bode well for the patient’s survival.

Symptoms may be ambiguous. Two common symptoms are jaundice and enlargement of the liver, with accompanying tenderness. Jaundice, a yellowing of the skin and eyes, is caused by an accumulation of bilirubin. Bilirubin builds up because a tumor has blocked the bile duct that normally empties it into the small intestine. (Both symptoms may also occur as a result of either gallstones or cirrhosis.) Patients with liver cancer may also have a fever and retain fluid in the abdominal cavities.

Treatment and Therapy

Doctors suspecting liver cancer conduct tests designed to distinguish this disease from other disorders. Palpation of the liver may reveal that the organ is enlarged or contains an unusual tissue mass, which is likely to be a tumor. A rubbing sound heard through the stethoscope may also come from a tumor. Hepatocellular carcinoma often elevates the alpha-fetoprotein level in blood. Abdominal ultrasound or computed tomography (CT) scans can provide good evidence of a tumor in the liver, and a biopsy will supply a tissue sample capable of proving the presence of cancer, especially if the biopsy is done with CT scan or ultrasound guidance. A tumor can also disrupt normal biochemical action in the body, which doctors may detect in blood tests. Liver function blood tests may be abnormal with both primary and secondary liver cancer.

Under even the most favorable circumstances, the outlook for patients with liver cancer is still not good. If a primary cancer is found while still fairly small, surgical removal is the surest and fastest treatment, although it is a difficult, risky procedure because of the liver’s complex, delicate structure. Radiation and chemotherapy have not succeeded in shrinking tumors effectively. Because symptoms usually appear late in the development of primary liver cancer, it seldom is found early enough for surgical cure; patients usually live only one to two months after detection. Those found with small, removable cancers live an average of twenty-nine months. Most liver cancers are metastases, however, and removal of the liver tumor will not rid the patient of cancer. In general, hepatobiliary cancer patients have low chance of living five years after diagnosis.

Liver cancer screening tests can locate tumors while they are still treatable, although routine physical examinations in Western nations seldom include such tests. Usually only patients with cirrhosis or chronic hepatitis are screened. The best ways to ward off liver cancer are to avoid viral infection and to abstain from alcohol. For those at risk for infection, such as health care workers, the most effective primary prevention is vaccination for hepatitis B. US cases of liver cancer are expected to rise by a factor of four during the second decade of the twenty-first century, primarily because of hepatitis C infections and "fatty liver" (which occurs in patients with diabetes and obesity).

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