New research published today in the British Journal of Cancer has found that women who experience a ‘false positive’ result following a mammogram are more likely to develop breast cancer later in life.

The study analysed screening data from 1,149,467 women in Denmark, Norway and Spain between 1991 and 2010. Across 3,510,450 screening exams, 113,634 women received a false positive result – with the largest proportion of these occurring in women aged 50-54.

Those who received one false positive were two times as likely to develop breast cancer compared to those who received a negative result. Women remained at an elevated risk for 12 years after their false positive result. Two false positives correlated to a four-fold increase in breast cancer risk compared to those with negative results.

Whilst the researchers say it isn’t clear why a false positive result confers a higher risk of developing breast cancer, it is hoped that in the future it may be a useful marker to predict which women may benefit from more frequent screening.

Baroness Delyth Morgan, Chief Executive at Breast Cancer Now, said:

These could be really important findings. Further investigation is needed, but this study suggests that a ‘false positive’ result may be able to act as a marker for women who could benefit from more frequent screening.

Crucially, we’d urge women who have received a false positive not to worry unnecessarily about their risk of developing breast cancer – but simply to attend screening when invited, check their breasts regularly and report any unusual changes to their GP. 

It’s important to note that this link represents a potential correlation but not a causation, and we hope further research will explain why women who receive false positive results may have a slightly increased risk of developing breast cancer. There could be a number of factors involved – for example, screening abnormalities could come as a result of women having a higher breast density, which is known to increase breast cancer risk.

Our risk of breast cancer can depend on a combination of our genes, family history, lifestyle, reproductive history and breast density. While there is much more research to be done, we are hopeful that tailoring screening to a woman’s individual risk could one day help detect more cases earlier, while enabling those at particularly low risk to avoid unnecessary screening.

The Breast Screening Programme remains absolutely critical to early diagnosis in this country, preventing 1,300 deaths from breast cancer each year. While screening comes with some risks to be aware of, we’d encourage all women to attend their appointments when invited.