What is HNPCC?
- HNPCC is a rare, 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 are found.
- 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 about 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 cancers can also occur in the kidney, urether (the tube
from the kidney to the bladder) and in parts of the gut such as the small
bowel (intestine), stomach or pancreas.
- In women frequent sites for cancer are the inner lining of the uterus (womb) and
the ovaries. The chance of developing these other cancers is not as high
as that of bowel cancer.
Treatment
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 to see a gynaecologist for an annual check-up
to assess the possibility of uterine cancer. Ovarian screening can also be
done at this time.
Gene testing
Researchers have identified some of the gene changes that cause HNPCC. If
you or a family member with HNPCC is found to have the gene change, other
family members also at risk of carrying the gene can be tested to establish
if they have inherited the gene change.
Sometimes the changed gene is not found after testing. This means that you
either do not have HNPCC or in your case, HNPCC was due to gene changes that
research has not yet identified. If no gene change is found, other family
members are unable to be tested.
A blood test is needed for gene testing. For further information, speak with
a local Genetic Counsellor.
