World Cancer Research Fund International estimated there was 14.1 million
new cancer patients around the world in 2012, with many of us having at least
one family member affected. However, when more than one relative develop
the same type of cancer, it’s normal to worry if it could be hereditary.
Cancers that seem to be hereditary are often caused by members of a family
being exposed to the same environmental carcinogen, e.g., cigarette smoke,
or sharing similar lifestyle factors, e.g., obesity, inactivity or unhealthy diets. In
other words, although several family members may develop breast cancer or
liver cancer, it doesn’t necessarily mean that the cancer has genetic roots.
Signs which may indicate familial cancer include several family members
developing a rare cancer, such as kidney cancer; cancers which occur in
paired organs, such as both breasts or eyes; or cancers which occur in a
much younger person than usual, for example, a young adult with colon
What are Inherited Cancers?
All cancers are caused by abnormal changes in genes, called mutations.
Mutations can be acquired or inherited, with most cancers being caused by
the former. Less commonly, certain cancers are caused by an inherited
abnormal mutation, which can be passed on from parent to child.
Scientists have identified over 50 types of inherited genetic mutations which
increase the risk of specific cancers. While not every condition can be tested
for, genetic testing is available for faulty genes linked to some cancers,
including breast cancer, bowel cancer, ovarian cancer and kidney cancer.
Breast cancer is one of the common cancers among women in developed
nations, but fewer than 3 in 100 cases are caused by faulty genes. The genes
linked to breast cancer which can be tested for are BRCA1 and BRCA2. While
it is rare to have faulty BRCA1 and BRCA2 genes, a very high percentage of
women who have either mutation develop breast cancer. These genes are
also linked to ovarian cancer. Men with faulty BRCA2 genes also have
increased risk of breast and prostate cancers.
Bowel cancer is mainly attributed to lifestyle factors such as eating red meat,
being overweight, having a low-fibre diet and drinking alcohol. However, some
5 in 100 cases are linked to faulty genes, which lead to benign growths in the
bowel. These growths can become malignant after many years. Several other
inheritable conditions, including Lynch Syndrome and Juvenile Polyposis
Syndrome, which are caused by faulty genes, can lead to bowel cancer.
Melanoma is a kind of cancer which most commonly affects the skin. While
most cases are attributed to sun or sunbed exposure, 10% of melanoma
cases appear to be inherited. If several members of your family have had
melanoma, you may consider getting tested specifically for faulty genes. A
condition called Familial atypical multiple mole melanoma syndrome also
carries a high risk of melanoma. This condition is diagnosed in people who
have a very large number of moles (over 50) on their body and have at least
one close relative who has had melanoma.
Deciding Whether to Get Tested
The decision to undergo genetic screening is a complicated and personal one,
yet one that will affect other family members. After a thorough review of your
medical history, you may be referred to a specialist or a genetic counsellor. A
counsellor can help you weigh the pros and cons of getting tested and discuss
the implications of a positive or negative result.
A negative result may ease your mind, but it doesn’t mean you won’t develop
a particular type of cancer. Likewise, a positive result doesn’t mean that you
will definitely develop it. Each condition comes with its own risks and benefits
related to testing.
For example, patients with faulty BRCA1 or BRCA2 genes may opt for a
double mastectomy to lower their cancer risk. However, with other conditions,
there may be no treatment options other than frequent screening. A positive
result can also have emotional effects, such as depression, or financial
implications, like difficulty in getting a mortgage. Therefore, testing should be
approached carefully and with professional guidance.
If you suspect that there may be a hereditary cancer in your family, see your
doctor to discuss your concerns. You may not require testing, or even if you
do, you may decide not to go ahead with it. However, as with other medical
concerns, seeking information is the first step towards making an informed