The ovaries of women with the BRCA1 mutation appear to have fewer eggs.
BRCA1 and BRCA2 mutations are associated with an increased risk of cancer in the breast, ovaries, fallopian tubes and peritoneum. The risk increases with age, and tends to be higher for people with BRCA1 genes.
In the general population, the prevalence of BRCA1 is around 0.1%, and for BRCA2, which is 0.2%, but some groups are more susceptible, such as Ashkenazi Jews.
According to the National Cancer Institute, about 12% of all women develop breast cancer at some point. However, 55-65% of people with a BRCA1 mutation and 45% of those with a BRCA2 mutation will develop by the age of 70 years.
Since cancers are difficult to detect treatable, earlier stages, women who have the mutation are sometimes advised to have children at a younger age and then undergo surgery to remove their ovaries and fallopian tubes when they reach 40.
However, there is little evidence of quality on the effects of mutations in BRCA1 and BRCA2 conditions that are not related to cancer, such as fertility.
AMH levels 25% lower in women with BRCA1 mutation
An international group of researchers, including first author Prof. Kelly-Anne Phillips, a medical oncologist consultant at the Peter MacCallum Cancer Centre in East Melbourne, Australia, looked at anti-Mullerian hormone (AMH) levels of 693 women, with an average age of 35 years, with no personal history of cancer.
AMH is known to be a reliable indicator of the amount of eggs in the ovaries of a woman.
Women, aged 25-45 years, were participants in a study from 1997 to 2012 by the Consortium Foundation of Australia and New Zealand Kathleen Cuningham for Research into Familial Breast Cancer (kConFab).
Basic facts about BRCA and ovarian cancer
- About 1.3% of women will develop ovarian cancer
- 39% of women with a BRCA1 mutation will develop ovarian cancer at the age of 70 years
- 11 to 17% of patients with a BRCA2 mutation develop ovarian cancer by age 70.
Among women with a family history of the BRCA1 mutation, 172 were carriers and 216 were not.
There were 147 carriers and noncarriers 158 families with the BRCA2 mutation.
The scientists conducted blood tests on women while pregnant or breastfeeding. All participants had both ovaries. The team adjusted for age, use of oral contraceptives, body mass index ( BMI ) and smoking.
The results showed an average concentration of AMH that was 25% lower in women with the BRCA1 mutation than in noncarriers. When women were divided into four groups according to the levels of AMH, women with the BRCA1 mutation were in the lowest quartile.
The same can not be said of the carriers of the BRCA2 mutation.
The team believes the results could be related to the role of the BRCA1 and BRCA2 genes in repairing breaks in both strands of the DNA helix. Previous studies have shown that inefficient DNA repair may lead to increased aging of eggs from a woman.
Prof. Philips explains that the role of BRCA2 in repairing breaks in double-stranded DNA is less important than that of BRCA1. BRCA2 carriers also develop fewer cancers and in a later age.
Therefore, he says, it seems plausible that BRCA1 would have a greater impact on ovarian reserve.
Add a BRCA2 mutation may also affect eggs lesser extent, but the current study was not sensitive enough to detect it.
Women with BRCA1 should consider that children previously
According to Prof. Philips, “Women in their 30s, who carry the BRCA1 mutation have, on average, similar to those of non-carriers that are two years older ovarian reserves.”
It adds that although AMH reliably reflects the number of eggs is only an indicator of fertility potential of women.
Other factors to consider include the quality of eggs and the presence of blockages in the fallopian tubes, AMH levels do not reflect.
Some women with low AMH levels can still conceive, while others with higher levels may be unable to do so.
However, based on current results, Prof. Philips suggests:
“Women who carry the BRCA1 mutation should try to avoid delay pregnancy until after 30 or 40 years when fertility is reduced anyway because of their age. For women trying conceive in their 20s, any differences in ovarian reserve between BRCA1 mutation carriers and noncarriers is unlikely to be of clinical importance. ”
Based on these findings, the authors speculate that women with the BRCA1 mutation undergoing cancer therapy may have an increased risk of chemotherapy-induced menopause because they have fewer eggs at the time of starting treatment.
However, they emphasize that more research is needed to confirm this hypothesis.
Medical News Today reported last year in suggestions that screening for BRCA is not profitable gene, due to its low prevalence in the general population.