Medical breakthroughs are making it possible to
manipulate the risk of breast and ovarian cancer in
women genetically predisposed, but detecting a faulty
BRCA1 gene – one of two gene faults linked to increased
likelihood of developing breast and ovarian cancer – is
less straightforward than it sounds.
Ordinarily charged with protecting against cancer,
BRCA genes are faulty in an estimated one in 800
Australian women. A faulty copy of one of four BRCA
genes–everyoneisbornwithtwocopiesofeach
the BRCA1 and BRCA2 gene – increases the risk of
developing breast and ovarian or fallopian tube cancer
by 60 to 80 per cent and 40 to 60 per cent respectively.
The most effective form of risk reduction for women
with a proven BRCA mutation is surgery to remove the
ovaries and fallopian tubes, usually before age 40. But
women who wish to stay fertile can use a combination of
oral contraceptive pills to reduce ovarian cancer risk by
50 per cent when used for at least five years.
While not as effective as surgery, there are other
options to minimise risk. Alternative preventative
options include regular mammograms or MRI scans
for early cancer detection and taking drug Tamoxifen,
which has been used as a treatment for breast cancer for
the last 30 years.
Certified gynaecological oncologist Dr Gregory
Gard says the most certain prevention against ovarian
cancer in women at high risk is removal of the tubes, as
it’s now recognised that most ovarian cancers occur in
the fallopian tube, not the ovary. So-called prophylactic
surgery reduces ovarian cancer risk from 30 to one or
two per cent, he says.
The removal of ovaries and fallopian tubes before
menopause also reduces breast cancer risk – although
not as much as the double mastectomy made famousby Angelina Jolie. The flip side is increased risk of heart
disease and osteoporosis according to Dr Gard, who
says hormone replacement therapy is imperative from
surgery until menopause age.SO HOW WOULD YOU KNOW IF YOU HAD A
FAULTY GENE?
The greatest risk factor for an errant BRCA1 or BRCA2
gene is family history according to geneticist associate
professor Judy Kirk from the University of Sydney.
Relatives who have experienced breast and/or ovarian
cancer on either parent’s side may indicate higher risk,
although there are multiple ifs and buts.
“If your mother was diagnosed over the age of 50
and no other family member has had breast or ovarian
cancer, the chance of you carrying a faulty BRCA1 or
BRCA2 gene is small, even if other family members
lived to an old age,” says Dr Kathy Tucker, head clinical
geneticist at the Prince of Wales Hospital. If your mother
experienced two separate breast cancer episodes or one
or more blood relatives had either breast or ovarian
cancer under the age of 40, however, your risk increases
and you may qualify for testing. Jewish lineage also
imposes a risk premium according to Dr Tucker.
If you are considered high risk, a GP may refer
you to a family cancer clinic for advice. However, it’s
not foolproof. “Sometimes even in families with the
strongest medical history we can’t always find the genetic
cause of cancers and the results aren’t meaningful
enough to take action,” Assoc Prof Kirk says. If a fault is
found, you and your other family members can be tested
to see if you have the same faulty gene. “We still don’t
always understand why in some families, for instance,
one sister will develop breast cancer at 30 years old and
another sister will never get it,” Assoc Prof Kirk says.Family
matters
DO YOU KNOW YOUR FAMILY HISTORY?
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