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Risk factors for extrahepatic bile duct cancer
A risk factor is something (such as a behaviour, substance or condition) that increases the risk of developing cancer. 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 incidence of extrahepatic bile duct cancer increases with age. Most people diagnosed with bile duct cancer are over 65. Bile duct cancer is slightly more common in men than women. Conditions that cause chronic inflammation of the bile ducts are associated with a higher risk of extrahepatic bile duct cancers.
The following are risk factors for extrahepatic bile duct cancer, which develops in bile ducts outside the liver. Find out more about risk factors for intrahepatic bile duct cancer.
Most of the known risk factors for extrahepatic bile duct cancer 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
|Known risk factors||Possible risk factors|
Known risk factors
There is convincing evidence that the following factors increase your risk for extrahepatic 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 (cholangitis) that leads to scar tissue (sclerosis). This condition increases the risk of bile duct cancers.
A choledochal cyst is an abnormal widening (dilation) of the bile ducts outside the liver. Choledochal cysts are rare and they are present at birth (congenital). People with choledochal cysts have an increased risk of developing bile duct cancer.
The pancreatic duct and the bile duct join outside the first part of the small intestine (duodenum). The point where these ducts join is called the pancreaticobiliary duct junction. A problem with this junction is called anomalous pancreaticobiliary duct junction. This abnormality is rare and is present at birth (congenital). It causes the digestive juices in the pancreas to flow back into the bile ducts rather than into the small intestine. This can lead to chronic irritation of the bile ducts.
People with an anomalous pancreaticobiliary duct junction have an increased risk of developing bile duct cancer.
Ulcerative colitis is chronic inflammation of the large intestine (also called the large bowel). People with this condition are prone to 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 associated 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 mediumcontrast mediumA substance used in some diagnostic procedures to help parts of the body show up better on x-rays or other imaging tests. in the 1950s. Thorotrast is no longer used because it increases the risk of developing extrahepatic bile duct cancer.
Possible risk factors
The following factors have been linked with extrahepatic bile duct cancer, but there is not enough evidence to say they are known risk factors. Further study 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, unhealthy amount of body fat. It may be a factor in the development of extrahepatic bile duct cancer because it is linked with non-cancerous (benign) gallbladder and biliary tract disease. People with extrahepatic bile duct cancer are more often overweight or obese than people who don’t have this disease.
Some studies have linked drinking alcohol to a higher risk of extrahepatic bile duct cancer. The risk is greatest among heavy drinkers, people with alcoholic liver disease and people with primary sclerosing cholangitis.
Some studies have shown that people with diabetes may have an increased risk of extrahepatic bile duct cancer, but the overall risk to someone with diabetes is low.
Unknown risk factors
It isn’t known whether or not the following factors are linked with extrahepatic bile duct cancer. It may be that researchers can’t show a definite link or that studies have had different results. Further study is needed to see if the following are risk factors for extrahepatic bile duct cancer:
- family history of extrahepatic bile duct cancer
- occupational exposure to chemicals
- oral contraceptives
- infection with hepatitis B virus or hepatitis C virus
- cirrhosis of the liver
Questions to ask your healthcare team
To make the decisions that are right for you, ask your healthcare team questions about risks.
Support from someone who has ‘been there’
The Canadian Cancer Society’s peer support program is a telephone support service that matches cancer patients and their caregivers with specially trained volunteers.