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New genetic test could reduce preventative mastectomies

October 12th, 2017

A genetic test that more accurately predicts the risk of developing breast cancer is being trialled on women at high-risk of breast cancer in the UK.

Currently all women who test positive for a BRCA gene mutation are given the same risk figure of 87 per cent, however calculating each person’s risk is actually much more complex and the percentage could be different for every individual.

Women at high risk of breast cancer who are found to have a faulty BRCA gene are given the option to have a mastectomy to drastically reduce their chances of ever developing breast cancer. But the concern is that many women are having mastectomies that they potentially do not need because their overall risk could be actually much lower than 87 per cent.

Women can make more informed choices

The new test takes a sample of blood to look at 18 genetic variations, including BRCA1 and BRCA2, known to affect a person’s chance of getting breast cancer.

During the study, the test was used to analyse the DNA of 451 women with a family history of breast cancer who had developed the disease. The researchers also included other risk factors such as breast density, family history, obesity and lifestyle to predict an overall estimate of each individual’s risk of developing breast cancer in their lifetime.

This process resulted in many of the women who were originally categorised as high-risk being reclassified as lower risk, which meant that surgery to remove their breast and reduce their risk was not a recommended next step and they could safely avoid it.

As such, the researchers say the test could reduce the number of women choosing to undergo pre-emptive mastectomy surgery from 50 per cent to about 36 per cent as they have a more accurate understanding of the role breast cancer may take in their future.

“BRCA1 and BRCA2 are just part of what we should be looking for when assessing risk. This new test will help women at risk of familial breast cancer to make more informed decisions about their care,” said Professor Gareth Evans, a medical genetics expert at the University of Manchester and Saint Mary’s hospital who led the research.