For the six-year study, 196 women with a BRCA1 or BRCA2 mutation, aged 21-68 years, underwent hospital check-ups every six months.
At the check-up, women were examined by a specialist, underwent mammography and, when possible, MRI.
During the study 81 women (41 per cent) had at least one positive MRI or mammogram. But just 17 women had breast cancer confirmed.
The probability of women having a false positive result was 83 per cent.
Dr James Mackay, a consultant genetic oncologist at University College London, said: ‘This clearly shows false positives are a problem.
‘It highlights how important it is to explain the possibility of false positives to patients undergoing imaging.'
In 2006, NICE recommended annual MRI screening for women with BRCA1, BRCA2 or TP53 mutations or a high family risk of breast cancer.
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