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Wednesday, 21 June 2017

21-07-2017 = Must read - 'Breast Cancer Genes': How Much Do They Increase Cancer Risk?


Women who carry genetic mutations in the
"breast cancer genes," called BRCA1 and
BRCA2, have about a 70 percent chance of
developing breast cancer in their lifetimes,
according to a new study.
The findings are based on an analysis of
nearly 10,000 women with mutations in
either the BRCA1 or BRCA2 gene , mutations
that are known to increase the risk of breast
and ovarian cancer. The new study is more
rigorously designed than some earlier
research that looked at how much the risk
for these cancers increases in women who
have these genetic mutations.
But the new study also found that breast
cancer risk in women with these mutations
could vary — by as much as twofold —
depending on whether the women had
specific mutations within their genes. In
addition, having close family members with
the disease also indicated a greater increase
in risk, the study found.
The findings suggest that health
professionals who council women who have
BRCA1 or BRCA2 mutations about their risk
of breast cancer should take into account
both a patient's family history and the
particular location on the gene of the
individual's mutation, the researchers said.
[6 Foods That May Affect Breast Cancer
Risk]
The findings "demonstrate the potential
importance of family history and mutation
location in risk assessment" of breast
cancer, the researchers said.
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Prior to the study, scientists knew that
women with mutations in the BRCA1 and
BRCA2 gene are at increased risk for breast
and ovarian cancer . Previous studies have
estimated that the lifetime risk of breast
cancer ranges from 40 to 87 percent for
women with BRCA1 gene mutations, and 27
to 84 percent for women with BRCA2 gene
mutations, according to the researchers. In
contrast, the average American woman has
about a 12 percent chance of developing
breast cancer by age 85, according to the
Susan G. Komen foundation, a nonprofit
organization that funds breast-cancer
research.
Many earlier studies on this topic were
"retrospective," meaning they included
information from women with these
mutations who already had breast or ovarian
cancer. Those studies used information
about the women's family history to help
estimate the genetic risk of these diseases.
But these estimates could have errors if
patients did not provide accurate family
histories — for instance, if the women
misremembered or didn't know that a certain
relative had breast cancer.
Accurate estimates of women's breast and
ovarian cancer risk are important because
they can help inform patients' decisions
about when to start getting breast or ovarian
cancer screenings, and whether to undergo
procedures to prevent cancer. Those
procedures can include having a double
mastectomy to prevent breast cancer.
The new study involved 9,856 women from
Europe, the United States, Canada, Australia
and New Zealand who had undergone
genetic testing and were found to have
genetic mutations in either the BRCA1 or
BRCA 2 gene. Of these women, about 4,800
had been diagnosed with either breast or
ovarian cancer before the study started,
while about 5,000 of the women had not
been diagnosed with either type of cancer.
The women were followed for about five
years to see if they developed cancer.
Most of the women were in their 40s or 50s
at the start of the study, although they
ranged in age from younger than 20 to older
than 70 years old. [5 Key Nutrients Women
Need as They Age]
The study found that:
Among women who had not been
diagnosed with breast cancer before the
study, those with BRCA 1 mutations
faced a 72 percent chance of
developing breast cancer by age 80, and
the BRCA2 carriers had a 69 percent
chance of developing breast cancer by
age 80.
Among women who had not been
diagnosed with ovarian cancer before
the study, the BRCA1 carriers faced a
44 percent chance of developing the
disease by age 80 and the BRCA2
carriers faced a 17 percent chance of
developing it.
Among women who'd already had
breast cancer in one breast, the risk of
developing cancer in the other breast
within 20 years was 40 percent for
BRCA1 carriers and 26 percent for
BRCA2 carriers.
The rate of new breast cancer cases
increased rapidly among younger
women, but leveled off around ages 30
to 40 years old for BRCA1 carriers and
40 to 50 years old for BRCA2 carriers.
The rate of new ovarian cancer
cases was low for young women but
rose as women reached their 40s and
50s.
The study also found that women with two
close relatives who had breast cancer (a
close relative could be a sister, mother or
aunt) were twice as likely to develop breast
cancer by the age of 70, compared to those
women with no close relatives with breast
cancer. And women with genetic mutations
located at a certain spots within the BRCA1
or BRCA2 genes were around 1.5 to 2 times
more likely to develop breast cancer,
compared to women with mutations located
at other places in the genes.
The researchers noted that their analysis
excluded women who had already undergone
a mastectomy (to reduce the risk of breast
cancer) or surgery to remove their ovaries
and fallopian tubes (to reduce the risk of
ovarian cancer). But the study was not able
to take into account whether the women
used certain medications, such as the
estrogen-blocker tamoxifen, to reduce their
risk of breast cancer.

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