Relatively few US women carry BRCA mutations
NEW YORK (Reuters Health) - A population-based study of black and white American women with and without breast cancer found that relatively few were carriers of mutations in BRCA1 or BRCA2 genes. Women who carry BRCA1 and BRCA2 gene mutations are more susceptible to developing breast and ovarian cancer.
"The high proportion of women in this study -- even those with a positive family history of breast cancer -- who were found not to carry a mutation in either gene serves as a continued reminder that most women with breast cancer are not carriers of mutations in these genes," Dr. Kathleen E. Malone told Reuters Health.
Malone, from the Fred Hutchinson Cancer Research Center, Seattle, Washington, and colleagues examined the frequency of BRCA1/BRCA2 mutations in "understudied racial and age groups." The study included white and black American women aged 35 to 64 -- 1628 with breast cancer and 674 without.
BRCA1 mutations were found more commonly in women with breast cancer (2.4 percent) than in controls (0.04 percent), the investigators report, as were BRCA2 mutations (2.3 percent vs. 0.4 percent).
Among all women with breast cancer, BRCA1 mutations were more likely to occur in women diagnosed at ages 35 to 44 years, those with a family history of ovarian cancer, and those with Jewish ancestry. The only factor significantly associated with BRCA2 mutations was early age of diagnosis.
Among women with breast cancer who also had a family history of breast cancer, four factors -- early diagnosis, Jewish ancestry, family history of ovarian cancer, and breast cancer in a relative before age 45 -- were strongly related to BRCA1 carrier status, the researchers note. Early age of diagnosis in the woman and early diagnosis in a relative were the only factors associated with BRCA2 mutations.
"Key hallmarks of an increased risk of being a BRCA1/BRCA2 mutation carrier among women with breast cancer include family history of ovarian cancer, early age (< age 45) of breast cancer diagnosis in a case herself or in a family member, and Jewish ancestry," Malone said.
"Women with breast cancer who have any of these characteristics are the most likely to benefit from genetic counseling and testing."
The researchers hope the findings "heighten awareness of family history traits and demographics that indicate a potentially heightened chance of carrying a mutation," Malone said.
"At the same time, it is important to remember that the presence or absence of any one factor does not equate necessarily with having a high or low risk of carrying a mutation and that it is important to consider a woman's entire family health history in the process of understanding risk."
There may be an impression that these genes "are not relevant to African-American women," Malone added. "Our findings disprove this. African-American women carry mutations at frequencies that are largely comparable to Caucasian-American women and most predictors of mutation status are of similar importance across racial groups."
SOURCE: Cancer Research, August 15, 2006.
What breastcancer.org says about this article…
Relatively few US women carry BRCA mutations
This study addresses two important misperceptions about the genetic mutations associated with breast cancer. That is, an abnormal BRCA1 or BRCA2 gene.
One is that all women (with and without breast cancer) tend to overestimate the likelihood that they could have an abnormal BRCA1 or BRCA2 gene.
The other misperception is that abnormal BRCA1 and BRCA2 genes are less common in African-American women.
This study showed that:
- Most women diagnosed with breast cancer (97.6%) do not have an abnormal BRCA1 or BRCA2 gene.
- A woman without breast cancer has a very low risk of having an abnormal BRCA1 or BRCA2 gene—less than 1%.
- African-American women have the same risk of having an abnormal BRCA1 or BRCA2 gene as white women.
The very small risk of having an abnormal BRCA1 or BRCA2 gene is higher in women (of any race) diagnosed with breast cancer who:
- have a family history of ovarian or breast cancer, or
- were diagnosed with breast cancer before age 45 or have a family member who was, or
- who are of Jewish ancestry.
Women of any race with breast cancer who have these characteristics are most likely to benefit from genetic counseling and testing.
