Key Points
- Lynch syndrome is a rare, inherited
condition that increases your risk of developing bowel cancer and sometimes
other cancers.
- Lynch Syndrome accounts for about 3%
of all bowel cancer.
- Regular bowel screening by colonoscopy
can prevent bowel cancers developing.
- Bowel Screening usually starts from
the age of 25 years and is performed on a yearly basis.
- People with Lynch Syndrome are also
at increased risk of developing certain other cancers such as uterine (womb),
urinary tract, ovary and small bowel.
- Women should consider screening of
the uterus and ovaries from the age of 30-35 years.
- Genetic testing is available for
families with this syndrome.
- When you have Lynch Syndrome, each of
your children have a 1 in 2 (50%) chance of inheriting it.
- The aim of the NZFGICS is to reduce
the number of cancers occurring in families by facilitating the required bowel screening for registered families.
What is
Lynch Syndrome?
Lynch syndrome is a rare inherited
condition that increases your risk of bowel cancer and other cancers. Lynch
syndrome has historically been known as Hereditary Non Polyposis Colorectal
Cancer (HNPCC). A number of inherited syndromes can increase your risk of bowel
cancer, but Lynch syndrome is the most common.
What is the
risk of developing bowel cancer in Lynch Syndrome?
The average New Zealander has about a
6% chance of developing bowel cancer by the age of 75 years but in Lynch
Syndrome there is up to a 50% chance of developing bowel cancer by the age of
70 years. Most bowel cancer normally occurs after the age of 50 years but in
Lynch Syndrome it occurs earlier.
What is the
risk of other cancers in Lynch Syndrome?
In some families with Lynch syndrome
there are other cancers, most commonly uterine or womb cancer, as well as bowel
cancer.
The average New Zealand woman has
less than a 2% chance of developing uterine or womb cancer but in Lynch Syndrome
this can be 30% or greater.
There is also an increased risk of
ovarian cancer, 3-13% by the age of 70 years compared to a risk of less than 2%
for the average New Zealand
women.
An increased risk of cancer at other
sites namely, urinary tract, small intestine, pancreas, brain and particular
types of skin cancers has also been found but by the age of 70 years the risk
of developing one of these cancers is estimated to be 10% or less.
Is the risk
of cancer the same for all families with Lynch Syndrome?
It is important to remember that not
all families have all cancers and that not all people develop every cancer that
can occur. In recent years it has been recognised that the risk of developing
both bowel and other cancers varies between families. This mostly relates to
the type of genetic spelling mistake in each family. Some people with Lynch
Syndrome will not develop cancer although they can still pass the gene mutation
on to their children.
What causes Lynch Syndrome?
Lynch Syndrome is caused by an abnormality in one of four mismatch
repair genes (MLH1, MSH2, MSH6, and PMS2). These are the genes responsible for
correcting mistakes that occur in genes when body cells divide.
More recently an error in a gene called EPCAM has been identified and
this also stops the MSH2 gene working properly meaning it can’t fix up those “spelling” mistakes.
Nearly every cell in our bodies contains two copies of each gene and
genes are the “instruction manuals” for building and running the body. DNA is
the genetic material within each cell that contains instructions for every
chemical process in the cells of the body. As cells grow and divide they make
copies of their DNA and it is common for minor mistakes to occur.
Normally the mismatch repair genes recognize these mistakes and repair
them, similar to the “spell check” function on your computer. However, people
who inherit a fault in one of the four mismatch repair genes lack the ability
to repair these minor mistakes. An accumulation of these mistakes may eventually
lead to the development of a cancer.
How is Lynch Syndrome inherited?
Lynch Syndrome is a condition that is passed from parent to child.
Occasionally it may occur “out of the blue‟ with no family history.
Each child of a parent with Lynch Syndrome has a 50:50 chance of
inheriting the genetic spelling mistake and each of those person’s children
then has the 50:50 chance of inheriting it.
This is called an autosomal dominant
inheritance pattern.
Do people who have NOT inherited the spelling mistake
need surveillance for cancer?
Children who do not inherit the gene cannot pass it on to their
children. They have the same risk as anyone else for developing cancer and
therefore do not need surveillance for the cancers linked with Lynch syndrome.
They should have the screening tests normally recommended by their General
Practitioners.
Is the risk of inheriting the condition different for
men and women?
The risk of inheriting Lynch syndrome is the same whether the gene
mutation carrier is the mother or father or if the child is a son or daughter.
What bowel checks are advised for individuals with
Lynch syndrome?
Most bowel cancer starts in polyps (called adenomas). In Lynch Syndrome
as the DNA “spell check” isn’t working and the time taken for a polyp to
develop into a cancer is sped up from the 5- 10 years it takes for bowel cancer
to develop in people with no family history of bowel cancer. This is the reason
why we currently recommend yearly colonoscopy for people with Lynch Syndrome.
A colonoscopy is a procedure which examines
the large bowel. If any polyps are detected they can be removed. Colonoscopies
can also detect bowel cancer at an early stage, when they are more treatable.
You need a colonoscopy every year, usually starting from the age of 25
years.
If a relative has had a bowel cancer
below the age of 35 years, we may begin screening in your family a bit earlier.
Do I need other checks?
For women we usually advise referral to a gynaecologist to discuss
checks that can be performed to look for uterine or ovarian cancer.
Screening for cancer of the uterus and ovarian cancer can begin around
the age of 30-35 years and is required every 1-2 years.
Uterine screening involves an ultrasound scan to measure the thickness
of the lining of the womb. It also involves taking samples of the lining of the
womb (pipelle).
Ovarian screening is usually done by an ultrasound scan.
Both of these procedures can be done as an outpatient procedure.
There is no evidence to support the effectiveness of this screening. The
screening for both uterine and ovarian cancer is less reliable than bowel
screening.
Some women may choose to have a hysterectomy (removal of the womb) and
oophorectomy (removal of the ovaries) rather than screening if they have
completed their families. We do not currently recommend this.
Check for the less common cancers in Lynch Syndrome may be recommended
and we will need to discuss this with you.
What about testing for my children?
When you have Lynch syndrome, each of your children have a 1 in 2 (or
50%) chance of inheriting the Lynch syndrome gene.
Children can be tested for Lynch syndrome once they reach the age of 18
years.
What about Genetic testing for family members?
If we have found a spelling mistake in one of the mismatch repair genes
that appears to be responsible for most of the cancer in your family we will
then let other family members know they can have a genetic test to see if they
too have inherited the gene alteration.
They need to understand the advantages and disadvantages of testing. It
is a very personal decision.
Some people decide to have a genetic test so they can decide about their
screening and to find out if there is a risk for their children.
Bowel screening by colonoscopy is not usually recommended in people
under the age of 25y and therefore many people delay having a genetic test
until this age.
People, who decide not to have genetic testing, should have regular
bowel checks every 2 years.
Does diet matter?
At the moment we do not really know the effect diet can have on the
development of cancers in Lynch Syndrome. However, we recommend that you have a
healthy diet and lifestyle. We also recommend that you maintain your body
weight within the healthy range recommended for your height.
For more information on diet Click Here
Is there medication available?
There is some evidence that aspirin
may reduce the chance of bowel cancer if taken regularly. This is something you
may wish to consider but you would need to talk this over with your General
Practitioner who knows your medical history and can help you decide if this is
appropriate for you.