A new study has estimated the ages at which women with BRCA 1 and 2 mutations are most at risk of developing breast and ovarian cancer.

The UK research found that the highest rates of breast cancer in women with the faulty BRCA1 gene were seen between the ages of 30 to 40. This peak occurred a decade later for those with a faulty BRCA2 gene.

Rates of ovarian cancer in women with either gene fault were highest between the ages 61-70.

The researchers believe the analysis could help women with a family history of the diseases make decisions around ways to reduce their risk.

The Cancer Research UK-funded scientists at the University of Cambridge followed nearly 10,000 women with BRCA1 or BRCA2 gene mutations. These faults can be inherited and are often found in women with a family history of breast and ovarian cancers.

Professor Arnie Purushotham, Cancer Research UK's senior clinical adviser, says: “Women who carry faulty BRCA genes are much more likely to develop breast or ovarian cancers, and this large study could help women, and their doctors, better understand their risk of developing these cancers.”

At the start of the study 5,046 of the women were free from cancer and 4,810 had breast or ovarian cancer, or both. During an average follow-up of 5 years, 426 women were diagnosed with breast cancer, 109 with ovarian cancer, and 245 with breast cancer in the breast opposite to the one in which cancer was previously diagnosed (contralateral breast cancer).

The researchers looked at the number of these cancers diagnosed across 10-year age groups over the course of the follow up period.

Key findings from the study which is published in the Journal of the American Medical Association, include:

  • Around 7 in 10 women with faults in either BRCA gene will develop breast cancer by the age of 80.
  • The cumulative ovarian cancer risk to age 80 years was 44 per cent for BRCA1 and 17 per cent for BRCA2 carriers.
  • After a first case of breast cancer, the risk of developing a tumour in the opposite breast within 20 years was 4 in 10 for women with BRCA1 faults and more than 2 in 10 for women with BRCA2 faults.
  • Around 4 in 10 women with faults in BRCA1, and fewer than 2 in 10 women with BRCA2 faults will develop ovarian cancer by age 80.
  • The breast cancer risk for women with either gene fault increases with the number of close relatives who have had the disease. Women with two or more such relatives had double the risk compared to those with no family history.

Professor Purushotham says, “This information could help women decide the steps that they may want to take to reduce their risk of breast cancer, such as preventative surgery, medication or lifestyle changes.”

The researchers say these are the most precise estimates of age-specific risks to date.

Only women with a strong family history of breast or ovarian cancer are tested for faulty genes in New Zealand. Visit the Genetic Health Service for more information: http://www.genetichealthservice.org.nz/

13 July 2017


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