Risk factors for bile duct cancer

A risk factor is something that increases the risk of developing cancer. It could be a behaviour, substance or condition. Most cancers are the result of many risk factors. But sometimes bile duct cancer develops in people who don’t have any of the risk factors described below.

The risk of developing bile duct cancer increases with age. Most people diagnosed with the disease are older than 65 years of age. Bile duct cancer is slightly more common in men than in women.

The following are risk factors for both extrahepatic and intrahepatic bile duct cancers. Some of the known risk factors are not modifiable. This means that you can’t change them. Until we learn more about these risk factors, there are no specific ways you can reduce your risk.

Risk factors are generally listed in order from most to least important. But in most cases, it is impossible to rank them with absolute certainty.

There is convincing evidence that the following factors increase your risk for bile duct cancer.

Primary sclerosing cholangitis (PSC) is an autoimmune disease (a disorder in which the immune system attacks healthy tissues in the body). It causes inflammation of the bile duct (called cholangitis) that leads to scar tissue (called sclerosis).

Choledochal cysts are abnormal widenings (called dilations) of the bile ducts outside the liver that are present at birth (congenital). Choledochal cysts are rare.

The pancreatic duct and the common bile duct join outside the first part of the small intestine (duodenum). Some people are born with a problem where these ducts join. When this happens, the digestive juices in the pancreas flow back into the bile duct rather than into the small intestine. This can lead to chronic irritation of the bile ducts, which increases the risk for bile duct cancer.

Ulcerative colitis is chronic inflammation of the large intestine (also called the large bowel). People with this condition often have primary sclerosing cholangitis (PSC), a strong risk factor for extrahepatic bile duct cancer.

Liver fluke is a type of parasite. There are many different types of liver flukes, but the ones most often linked with extrahepatic bile duct cancer are Clonorchissinensis (C. sinensis) and Opisthorchisviverrini (O. viverrini). Liver fluke infections are more common in some parts of Asia. People get the infection by eating raw or undercooked freshwater fish that contain the flukes. These parasites lead to chronic inflammation of the bile duct.

Thorium dioxide (Thorotrast) is a radioactive solution that was used as a contrast medium in the 1950s. Thorium dioxide is no longer used because it increases the risk of developing bile duct cancer.

People with diabetes have a slightly higher risk of developing bile duct cancers. The number of people with diabetes who develop bile duct cancer is still very low.

1,2-dichloropropane (1,2-DCP) is a chemical used in some types of offset printing. Studies show that people exposed to 1,2-DCP have a higher risk for bile duct cancers and are more likely to develop them at a younger age.

Chronic infection with hepatitis B virus (HBV), hepatitis C virus (HCV) or both viruses increases the risk of developing intrahepatic bile duct cancer. HBV can be spread from person to person through blood or other body fluids, such as semen or vaginal fluids. HCV is spread only through contact with infected blood.

The following factors have been linked with bile duct cancer, but there is not enough evidence to show they are known risk factors. More research is needed to clarify the role of these factors for bile duct cancer.

Obesity is a condition in which a person has an abnormally high and unhealthy amount of body fat. Bile duct cancer seems to develop more often in people who are overweight or obese.

Some studies link drinking alcohol to a higher risk for bile duct cancer. The risk seems to be greatest among heavy drinkers, people with alcoholic liver disease and people with primary sclerosing cholangitis.

Cirrhosis is when scar tissue replaces healthy liver tissue. The scar tissue blocks blood flow through the liver so it can’t function normally. Cirrhosis is caused by long-term damage to liver tissues, such as drinking too much alcohol or being infected with hepatitis B or C viruses. Research shows that cirrhosis can increase the risk for liver cancer, but studies are still trying to find out if it increases the risk for bile duct cancers.

Some studies link smoking to a higher risk for bile duct cancer.

It isn’t known whether or not asbestos is linked with bile duct cancer. It may be that researchers can’t show a definite link or that studies have had different results. More research is needed to see if asbestos is a risk factor for bile duct cancer.

To make the decisions that are right for you, ask your healthcare team questions about risks.