Breast cancer survivors
Triple negative breast cancer
Women under 45
Women over 45
Special populations: Bahamian women
The Bahamas has the highest known frequency of BRCA mutations among people diagnosed with breast cancer. This study reviewed whether population-based BRCA testing (testing everyone regardless of family or personal history of cancer) would be an effective approach for finding mutation carriers in the Bahamas. (3/4/19)
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Whether population-based BRCA testing (testing everyone regardless of family or personal history of cancer) would be an effective approach for finding mutation carriers in the Bahamas.
The Bahamas has the highest percentage of breast cancer patients who test positive for a BRCA mutation. Prior studies have shown that over 25 percent of patients with breast cancer in the Bahamas have a BRCA1 or BRCA2 mutation. Experts have proposed testing all women in the Bahamas with breast or ovarian cancer for BRCA mutations.
Over 1,800 unaffected Bahamian women underwent genetic testing. Of these:
This study suggests that in addition to testing women diagnosed with cancer, all Bahamian women with a family history of breast or ovarian cancer should also be offered genetic testing. If you are a woman from the Bahamas with a family or personal history of breast or ovarian cancer, you should speak with your doctor about genetic testing for a BRCA1 or BRCA2 mutation.
The Bahamas has the highest prevalence of BRCA mutations among breast cancer patients. In one study, one of the six BRCA1 founder mutations was identified in 49 (23%) of 214 unselected Bahamian breast cancer patients. In a follow-up to this study, researchers conducted full sequencing for BRCA1 and BRCA2 for the 156 patients who did not have a known BRCA1 founder mutation. Four of these patients were found to have a novel founder mutation in BRCA2; five other unique mutations in BRCA1 and BRCA2 were also identified. In total, mutations were discovered in 58 of the 214 patients (27%). This prevalence far exceeds that of any other population.
In comparison, the reported BRCA prevalence in Ashkenazi Jewish women is between 1% and 2% , with three known founder mutations accounting for the majority of BRCA mutations in this population. NCCN guidelines recommend testing for unselected Jewish women who have a personal history of breast cancer. Many genetics experts believe that the high prevalence of BRCA mutations in Jewish women and the ability to test for specific founder mutations makes population-based screening cost effective. (It is important to note that not all women with a BRCA mutation have a family history of breast and/or ovarian cancer. This is especially true for women with a limited number of female relatives.)
Because the prevalence of BRCA mutations among breast cancer patients in the Bahamas is higher than any other population, researchers sought to determine whether population-based testing is an effective approach to BRCA testing in the Bahamas.
If they could generate evidence to help inform an effective BRCA testing policy for Bahamian women.
These researchers screened a large sample of Bahamian women with no personal history of breast or ovarian cancer. These included both women with and women without a family history of cancer.
Personal and family histories of cancer were collected during pre-test genetic counseling.
A total of 1,921 unaffected Bahamian women provided a saliva sample from which DNA was isolated. Of these women, 44 were not screened for one of the seven founder mutations due to low quality DNA; 30 other participants were excluded because their family cancer history was unknown.
A total of 1,847 unaffected Bahamian women underwent genetic testing:
In this study, 2.8% of women with a first- or second- degree relative with breast or ovarian cancer had a Bahamian founder mutation.
The patients in this study-mostly were employees of a large resort-were self-selected and did not represent a random sample. Participants were asked about their Bahamian ancestry, however, this information was not verified. Finally, testing in this study was limited to the seven Bahamian founder mutations; participants may have had other deleterious BRCA mutations.
The results of this study support a policy to extend genetic testing for the seven Bahamian BRCA1 and BRCA2 founder mutations to all Bahamian women with a family history of breast or ovarian cancer.
It is important to note that unaffected Bahamian women without a family history of breast or ovarian cancer rarely have a BRCA mutation (0.09% in this study). It is unclear why the prevalence of mutations in unselected breast cancer patients would be so high compared to a relatively low prevalence in the general population.
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