Women should be aware of unnecessary mastectomies due to the ‘Jolie effect’, according to experts.
Females with mutations in the BRCA1 gene, such as Hollywood actress Angelina Jolie, and the related BRCA2 gene, are at greater risk of breast cancer.
But a study has now found their risk is 76 per cent higher if they also have a mother or sister with breast cancer.
Experts are concerned women may not realise their risk of breast cancer is far higher if they have a family history, like Ms Jolie, who had a mastectomy to reduce her risk of developing cancer.
Those without a family history may end up having surgery to protect against cancer, making the important decision without realising they are far less likely to get it.
Females with mutations in the BRCA1 gene, such as Hollywood actress Angelina Jolie (pictured in 2021), and the related BRCA2 gene, are at greater risk of breast cancer
The evidence comes from a study of 450,000 British people, aged 40 to 70, who were given genetic tests as part of the UK Biobank health study.
These included 230 with a mutation in the BRCA1 gene, of whom 78 also had a mother or sister who had breast cancer.
When these people were tracked up until the age of 60, almost 45 per cent with the genetic mutation and a family history developed breast cancer.
But only 23 per cent of women with the mutation got breast cancer before the age of 60 if they did not also have a close family history of it.
The researchers say women should pay close attention to the figures, as the rise of genetic testing kits taken at home means many can now find out they have a mutation in one of the BRCA genes.
Experts are concerned about the decisions that could be made by these women, who would not have been eligible for a genetic test through the NHS unless they had breast or ovarian cancer, or a family member with either of these cancers and a known BRCA mutation.
Hollywood star, Ms Jolie (pictured in 2011), had a mastectomy to reduce her risk of developing cancer
The researchers say women should pay close attention to the figures, as the rise of genetic testing kits taken at home means many can now find out they have a mutation (Stock Image)
Dr Leigh Jackson, who led the study from the University of Exeter, said more women were choosing breast cancer surgery, particularly since Angelina Jolie, 48, shared her experience.
But he added: ‘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.
‘We’d urge that anyone communicating cancer risk does so based on a detailed family history, not just genetics alone.’
The study, published in the Lancet journal eClinical Medicine, said estimates of breast cancer risk from genetic mutations like BRCA1 and BRCA2 may be misleadingly high for people without a family history of the disease.
That is because people with a family history probably have a higher risk from unknown mutations in genes besides the BRCA genes.