What is HNPCC?

Hereditary Cancer Registry
Hereditary non-polyposis colorectal cancer (HNPCC)

What is HNPCC?

• HNPCC is an inherited bowel cancer syndrome that accounts for approximately 1-5% of bowel cancers.
• Although the name — hereditary non-polyposis colorectal cancer — suggests people will not develop polyps, people affected by HNPCC are at risk of developing bowel polyps, just in small numbers. The term “non-polyposis” is used to distinguish HNPCC from another hereditary bowel cancer condition called FAP, in which 100s to 1000s of bowel polyps develop.
• HNPCC is caused by a change in a gene that normally functions to protect a person from getting cancer. If you have a parent or sibling with HNPCC, you are potentially at risk of developing HNPCC. If you have been diagnosed with HNPCC, your children are at risk. When a parent carries the changed gene, they have one working and one non-working copy of the HNPCC gene. Each child will independently have 50% chance of inheriting the gene fault.
• Not everyone with the gene change will develop bowel cancer. A person who inherits this gene change has up to an 80% chance of developing bowel cancer by the time they are aged 80 unless preventative measures are taken. Developing bowel cancer at a young age is not uncommon.
• Not all people with HNPCC have a family history of HNPCC. Some people may be the first in their family to get HNPCC. If you are the first one in your family to get HNPCC, each of your children still have the same 50% chance of inheriting the gene change.
• In men and women with HNPCC, cancers can also occur in the kidney, ureter (the tube from the kidney to the bladder) and in parts of the gut such as the small bowel (intestine), stomach or pancreas.
• Women also have an increased risk of cancer of the inner lining of the uterus (womb) and the ovaries, although the risk of bowel cancer is higher.

Management

Regular check-ups

If you are a member of a family affected by HNPCC you should have regular bowel screening beginning in your early to mid-20s. For this procedure – called a colonoscopy – a specialist uses a long flexible tube to examine the lining of your colon (large intestine) for any polyps or signs of cancer.

Women from the age of 35 may need annual screening of the uterus and ovaries in the form of ultrasounds and blood tests.

Genetic testing

• Researchers have identified some of the gene changes that cause HNPCC.
• If a gene change is identified amongst your family (in someone who has HNPCC), other relatives at risk of carrying the gene change can be tested.
• Sometimes the changed gene is not found in the family. This means that in your case, HNPCC may be due to other gene changes that research has not yet identified. If the family gene change is not found, genetic testing is not able to be offered to other family members.
• If a family gene change is found, the rest of the family can be offered predictive testing. This means testing to see if you have inherited HNPCC by checking whether or not you have the gene change even though you may not have any signs or symptoms yet.
• A blood test is needed for genetic testing. For further information speak with a Genetic Counsellor.

For more information on Cancer Genetics and hereditary cancer, please visit CI-SCaT and click on the patients & carers tab.