BRCA1 Mutation Linked to Fewer Eggs in Ovaries

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Most inherited cases of breast cancer are associated with two abnormal genes: BRCA1 (BReast CAncer gene one) and BRCA2 (BReast CAncer gene two). It’s been estimated that women with an abnormal (also called mutated) BRCA1 or BRCA2 gene have up to an 85% risk of developing breast cancer by age 70. These women’s risk of ovarian cancer also is higher than average.

About 2% of all people with breast cancer have an abnormal BRCA1 gene. But the percentage of women with an abnormal BRCA1 gene is higher in women diagnosed at a young age and women diagnosed with triple-negative breast cancer.

Triple-negative breast cancer is cancer that is estrogen-receptor-negative, progesterone-receptor-negative, and HER2-negative.

A study suggests that women with a BRCA1 mutation have fewer eggs in their ovaries.

The research was published online on April 19, 2016 by the journal Human Reproduction. Read the abstract of “Anti-Müllerian hormone serum concentrations of women with germline BRCA1 or BRCA2 mutations.”

Anti-Müllerian hormone (AMH) is produced by the ovarian follicles, which are the cells that surround each egg in a woman’s ovaries. AMH levels tell doctors how many eggs are left in a woman’s ovaries. AMH levels are measured by a blood test.

Normal BRCA1 genes make enzymes that help with DNA repair. Research suggests that less than optimal DNA repair, which happens when a BRCA1 gene has a mutation, may contribute to the premature aging of a woman’s eggs.

In this study, the researchers looked at AMH levels from 693 women ages 25 to 45 who were part of the Australian and New Zealand Kathleen Cuningham Foundation Consortium for Research into Familial Breast Cancer study, also known as the kConFab study. The women had never been diagnosed with cancer, but all the women came from families that were known to have a BRCA1 or BRCA2 mutation:

  • 172 women had a BRCA1 mutation and 216 women didn’t
  • 147 women had a BRCA2 mutation and 158 women didn’t

All the women had both their ovaries and none of them were pregnant or breastfeeding when blood was drawn to measure AMH levels.

The researchers found that women with a BRCA1 mutation had AMH levels that were 25% lower, on average, than women from BRCA1 families who didn’t have the mutation.

"This means that women in their mid 30s who carry the BRCA1 mutation, have, on average, ovarian reserves similar to those of non-carriers who are two years older," said Dr. Kelly-Anne Phillips, medical oncologist at the Peter MacCallum Cancer Center in East Melbourne. “Our findings suggest that women carrying the BRCA1 mutation should try to avoid delaying pregnancy until their late 30s or 40s when fertility is reduced anyway because of their age. For women trying to conceive in their 20s, any difference in ovarian reserve between BRCA1 mutation carriers and non-carriers is unlikely to be of clinical significance.

"Still, it's important to remember that AMH is only one indicator of a woman's potential fertility," she added. "The ability to conceive and carry a baby to full term is affected by many other factors as well, including egg quality and whether the fallopian tubes are unobstructed, neither of which are measured by AMH. Women with low AMH levels can sometimes still have a baby, and, conversely, women with high AMH levels are sometimes unable to do so."

There was no difference in AMH levels between women with a BRCA2 mutation and women from BRCA2 families who didn’t have the mutation.

The researchers also said that the findings raise another question: Do women with BRCA1 mutations have a higher-than-average risk of chemotherapy-induced menopause?

"The hypothesis is that if BRCA1 mutation carriers have lower ovarian reserve than their non-carrier counterparts when they start chemotherapy for cancer treatment, the carriers may be more likely to develop menopause associated with the chemotherapy," said Phillips. "However, this is just a hypothesis at this stage and requires further research."

If you know you have a BRCA1 mutation and plan on having children, you might want to talk to your doctor about this study and ask what it means for your unique situation. You may want to have your AMH levels checked before you try to conceive or ask for a referral to a fertility specialist if you’ve been having problems conceiving.

And stay tuned to the Breastcancer.org Research News pages for the latest information on BRCA1 mutations and fertility issues.



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