Brest Cancer
The
Odds of Having Abnormal Breast Cancer Genes
Most
women who get breast cancer do NOT have an inherited abnormal
breast cancer gene. BRCA1 and BRCA2 abnormalities probably
account for only about 10% of all breast cancers.
The
abnormal breast cancer genes were first discovered in studies
of families in which many young women were affected by breast
cancer, ovarian cancer, or both.
You
are more likely to have an abnormal breast cancer gene if:
* You have blood relatives (grandmothers, mother, sisters,
aunts) on either your mother's or father's side of the family
who had breast cancer diagnosed before age 50.
* There is both breast and ovarian cancer in your family,
particularly in a single individual.
* Women in your family have had cancer in both breasts.
* You come from an Ashkenazi Jewish family (family from
Eastern Europe).
* A man in your family has had breast cancer.
If
one family member has an abnormal breast cancer gene, it
does not mean that all family members will have it.
Suppose
either your mother or father has a BRCA1 or BRCA2 abnormality.
Your chance of inheriting the abnormal gene is 50%. Each
of your children has a 25% chance of inheriting the abnormal
gene—50% of your 50% risk (as long as the children's father
does not have an abnormal gene).
Abnormalities
seen more in younger women
Breast
cancer gene abnormalities are more commonly found in women
diagnosed with breast cancer before age 40. As many as 25%
of these women have an abnormal breast cancer gene—usually
BRCA1—regardless of their family history.
Gene
abnormalities in Ashkenazi Jewish women
Specific
abnormalities in the BRCA1 and BRCA2 genes are more commonly
found in Ashkenazi Jewish women, than in other women. Ashkenazi
Jews have ancestors from Central or Eastern Europe. Many
other ethnic and racial groups whose members tend to inter-marry
and have children also have specific genetic abnormalities.
About
1 in 40 Ashkenazi Jews—with or without breast cancer—has
a genetic mutation in BRCA1 or BRCA2. In one study of more
than 5,300 Ashkenazi Jewish men and women (New England Journal
of Medicine, May 15, 1997), 120 people (2.3%) had one of
the three specific abnormalities in BRCA1 and BRCA2 known
to be associated with a higher risk of breast cancer.
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The information on this page has been extracted from http://www.breastcancer.org/
genetics_odds_abnormal_genes.html.
