Screening for breast cancer genes could be leading women to undergo needless mastectomies, experts have warned.
A new study by the University of Exeter has found that the risk of developing cancer by the age of 60, if carrying the BRCA1 or BRCA2 gene, is as low as 18 per cent, but women are being led to believe it is as much as 80 per cent.
Women, including the actress Angelina Jolie have chosen to have breast surgery to prevent cancer based on screening for the gene mutations.
But researchers warned that the risk has been calculated based on women who were screened for BRCA because they had already had breast cancer symptoms or a family history of the disease.
To find out the true underlying risks, the team analysed more than 454,000 participants of the UK Biobank study, aged between 40 and 69.
They found that even if a woman has BRCA mutations, her risk is relatively low unless she also had a close relative with breast cancer.
Simply carrying a disease-causing BRCA variant was linked to a breast cancer risk of 18 per cent for BRCA2 and 23 per cent for BRCA1 by the age 60.
Having a close relative who has had the condition elevated the risk to 24 per cent, for BRCA2 and 45 per cent for BRCA1.
‘We want women to make an informed decision’
Dr Leigh Jackson, of the University of Exeter Medical School, said: “Being told you are at high-genetic risk of disease can really influence levels of fear of a particular condition and the resulting action you may take.
“Up to 80 per cent risk of developing breast cancer is very different from 20 per cent. That difference could well influence the decision you make around whether you have invasive breast surgery.
“Some women may decide to go ahead with that procedure knowing that the risk is 20 per cent, but we want them to make an informed decision. We’d urge that anyone communicating cancer risk does so based on a detailed family history, not just genetics alone.
“If you’re given a high-genetic risk of any disease outside of a clinical setting, we’d advise you to speak to your doctor, who will be able to take into account a range of factors, including family history, to assess whether the risk may be worth investigating further.”
Ms Jolie, who carried BRCA1, opted for a prophylactic double mastectomy after being told her risk of breast cancer was 87 per cent. Jolie’s mother died of ovarian cancer at age 56.
Currently the NHS only offers screening for BRCA if a relative has the gene mutation or if there is a strong family history of breast cancer, although charities have called for its wider adoption.
But many women are finding out they have the mutation through home testing DNA kits, or by taking part in genetic research.
Experts warned that women could be opting to have unnecessary surgery after being told they are at high risk from genetic test results which do not take family history into account.
Findings do not apply to just breast cancer
The research team found a similar result when looking at genetic risk of Lynch syndrome, a genetic condition which increases the risk of colon cancer and some other cancers.
The authors concluded that genetic screening in the general population could result in large numbers of people being exposed to needless scans or further procedures.
The study’s co-author Professor Caroline Wright, of the University of Exeter Medical School, said: “Our findings will not just apply to breast and colorectal cancer.
“All risk-estimates of genetic disease have so far largely been based on relatively high-risk groups who attend specialist clinics, so they will not necessarily translate to the general population.
“This finding has important ramifications for population screening using genome sequencing.
“We need to ensure we are carrying out research to find the true risk level, and also to be responsible in how we communicate risk, to avoid unnecessary fear and distress which may lead to avoidable procedures.”
The warning has emerged in a paper published today in the Lancet journal eClinicalMedicine.