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Women with
BRCA1 and BRCA2 mutations have an average risk of 72% and 69% respectively of developing
breast cancer by the age of 80. The corresponding life time risks for ovarian
cancer is 44% for BRCA1 and 17% for BRCA2 says the results of first ever
prospective study published June 20, 2017 in JAMA.
BRCA1 was
first discovered 23 years ago in 1994 by Mary-Claire King, professor of genome
sciences and of medicine at University of Washington, BRCA2 followed later.
Today it is
an established fact that women who test positive for BRCA mutation are not only
at increased risk for breast cancer but also at increased risk for ovarian
cancer, but all the studies so far have been retrospective in nature.
According to NIH, together, BRCA1 and BRCA2 mutations account for
about 20 to 25 percent of hereditary breast cancers and about 5 to 10 percent
of all breast cancers. Similarly, mutations in BRCA1 and BRCA2 account for
around 15 percent of ovarian cancers.
This current
prospective study was made possible by collaboration between researchers at
Australia, Europe and USA. The team recruited 10,000 women with BRCA1(6036) and
BRCA2 (3820) mutations from 1997 to 2011 from various registries across U.K,
Netherlands and France.
Some very
important findings of the study are:
Women with BRCA1 and BRCA2 mutations have an average risk of 72% and 69% respectively of developing breast cancer by the age of 80. The corresponding life time risks for ovarian cancer is 44% for BRCA1 and 17% for BRCA2
Of nearly
10,000 women, 5046 were unaffected and 4810 were diagnosed with breast or
ovarian cancer or both at baseline.
At follow
up, 11% of women developed breast cancer, 2% developed ovarian cancer and 11% were affected with contralateral breast cancer.
The median
age of women at diagnosis of the breast and ovarian cancer was 38 years and 47
years for contralateral breast cancer.
Another
important finding in the study was, breast cancer risk for women with faults in
BRCA1 increases till age 40, and for BRCA2 it increases till age 50 years of age
and then remains constant high level for the rest of their lives.
The risk of
getting a diagnosis of second breast cancer for contralateral breast up to 20
years of first cancer was 40% for BRCA1 carriers and 26% for BRCA2 carriers.
The
incidence of ovarian cancer increased with age up to 61 to 70 years for both
mutations but was about 3 times higher for BRCA1 carriers.
The risk of
breast cancer nearly doubles for both BRCA1 and BRCA2 carriers, with an
increase in number of first and second-degree relatives having breast cancer.
The lead
author, Antonis Antoniou, PhD, from the Centre for Cancer Genetic Epidemiology,
University of Cambridge, United Kingdom explained "This is important
information to inform the clinical management also of women with mutations over
the age of 60 years old."
The study also
revealed that the risk for breast cancer is stratified according to location of
the mutation in certain regions, but location did not appear to affect the risk
for ovarian cancer.
Dr Antoniou said,
"The results from this study show clearly, and again for the first time in
a prospective study, that the cancer risks for women with BRCA1 and BRCA2
mutations depend on the position of the specific fault within the gene."
"Moreover,
the study provides for the first-time cancer risk estimates for mutations at
different locations," he added. "Therefore, mutation location can now
be confidently incorporated in the risk assessment of women with BRCA1 and BRCA2
mutations."
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This study
has important implications for physicians in clinical practice as they can
improve the advice and counselling, precisely pointing at the risk faced by the
women. It also emphasizes the importance of family history and following the
risk reducing life style changes.
Dr Antonis
Antoniou says, "We have been able to provide the most precise estimates of
age-specific risks to date. These should provide more confidence in the
counseling and clinical management of women with faults in the BRCA1 and BRCA2
genes."
The strengths of the study are its prospective nature, prolong follow-up and large data base because of sharing of data across multiple centers.
