Current guidelines for breast cancer screening in women under 50 in the UK are failing to identify the vast majority of those at higher risk, according to a new study. Researchers warn that up to 95% of younger women who are at increased risk of developing the disease are being missed by the existing criteria.

The National Institute of Health and Care Excellence (Nice) guidelines primarily focus on inherited genes when assessing risk for this age group. However, the study, published in the British Journal of Cancer, highlights that most breast cancer cases in women under 50 are not linked to genetic predispositions.

A new risk assessment tool, developed by researchers from Cambridge University and the Institute of Cancer Research, was used in the study. This tool, called Boadicea, incorporates a wider range of factors including family history, lifestyle choices, reproductive history, and genetic information. Using this comprehensive approach, the study identified eight times as many women under 50 who developed breast cancer compared to current referral rates.

The implications of these findings suggest a significant gap in the current screening strategy. If implemented, the Boadicea tool estimates that approximately 26.5% of women under 50 could be categorized as above-average risk and referred for further assessment. This contrasts sharply with the 1.4% of women currently referred under the Nice guidelines.

A key reason for this discrepancy is that a substantial majority, about 73%, of women under 50 who develop breast cancer within a decade have no family history of the disease. This makes the current Nice criterion of focusing on family history insufficient for identifying many at-risk individuals.

Lead researcher Dr. Juliet Usher-Smith stated that the NHS should review its criteria in light of these findings. However, she also acknowledged the potential challenges, such as increased workloads for healthcare professionals and the possibility of causing unnecessary anxiety and checks for some women.

Dr. Sowmiya Moorthie from Cancer Research UK, which funded the research, emphasized the need for any changes to be accessible and equitable, carefully considering the emotional impact on women who might be referred for extra checks. She also noted that existing risk calculators, including Boadicea, are not perfect.

Nice has acknowledged the findings and the potential of multifactorial risk assessment tools. However, the body stated that the current evidence does not yet warrant a change to its breast cancer screening guidelines for women under 50.