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Latest research 27 Jun 2017

New study on BRCA risks

A large international study of 9,856 women with a BRCA1 or BRCA2 gene mutation, including women from Australia, has given researchers a new understanding of the risk of developing breast and ovarian cancer for those who carry a BRCA1 or BRCA2 genetic mutation.

The study followed 6,036 women with a BRCA1 gene mutation and 3,820 women with a BRCA2 gene mutation recruited from 1997 to 2011 to better understand the risk of developing breast cancer, ovarian cancer and contralateral breast cancer (i.e. breast cancer in the other breast) in BRCA1 and BRCA2 mutation carriers. Of the 9,856 women, 4,810 had a previous diagnosis of either breast cancer, ovarian cancer or both at the time they were recruited to participate in the study, while 5,046 women had no prior diagnosis.

The study found that:

  • For women with a BRCA1 gene mutation
    • the risk of developing breast cancer by the age of 80 was 72%
    • the risk of developing ovarian cancer by the age of 80 was 44%
    • the risk of developing contralateral breast cancer 20 years after an initial breast cancer diagnosis was 40%
  • For women with a BRCA2 gene mutation
    • the risk of developing breast cancer by the age of 80 was 69%
    • the risk of developing ovarian cancer by the age of 80 was 17%
    • the risk of developing contralateral breast cancer 20 years after an initial breast cancer diagnosis was 26%.

The researchers also found that a woman’s age affected her risk. The risk of developing breast cancer ‘increased rapidly’ through young adulthood, before plateauing. For women with a BRCA1 mutation, the risk plateaued at between 31 and 40 years of age; for those with a BRCA2 mutation, the risk plateaued five to ten years later. 

Having other family members diagnosed with breast cancer was found to further increase the risk of those with BRCA1 and BRCA2 gene mutations. The location of a mutation on a BRCA1 and BRCA2 gene was also found to impact an individual’s cancer risk. The researchers note that the study shows the ‘potential importance of family history and mutation location in risk assessment’.

Researchers from Peter MacCallum Cancer Centre, the University of Melbourne and Cancer Council Victoria were part of the international collaboration. Discussing the impact of the study, Melbourne-based researcher Professor Kelly-Anne Phillips noted: ‘This study provides us with much more precise information about cancer risks for carriers and will help personalise decision-making about the use and timing of prevention strategies such as medication, surgery and changing lifestyle factors.’

More information 

For more information on family history and inherited gene mutations, read BCNA’s Family history fact sheet.

For more information about the study