False positive results on mammogram negatively impact screening behaviour

20170217140500, Roshini Claire Anthony

Women who received a false positive result on their previous mammogram were less likely to undergo timely subsequent screening than women who obtained a true negative result, a recent study showed.

Women who received a true negative result from the index mammogram were more likely to undergo a subsequent mammogram than those who received a false positive result (85.0 percent vs 77.9 percent; p<0.001), and also had a higher likelihood of undergoing a subsequent screening in the next 36 months compared with women who had a prior false positive result (adjusted hazard ratio, 1.36, 95 percent confidence interval, 1.35–1.37; p<0.001). [Cancer Epidemiol Biomarkers Prev 2017;doi:10.1158/1055-9965.EPI-16-0524]

Women who had a false positive result on their prior mammogram also delayed subsequent screening (a subsequent mammogram carried out >12 months after index mammogram) compared with women who had a true negative result (median 13 vs 3 months delay; p<0.001).

Women who had to undergo additional imaging had a 24 percent lower chance of subsequent screening, while those who had both additional imaging and biopsy had a 34 percent lower chance of subsequent screening compared with women who did not require additional tests.

Among women with false positive results, those who had to undergo additional imaging tests as well as biopsy had a 19 percent lower chance of subsequent screening compared with women who only underwent additional imaging.

Women with false positive findings in their initial mammogram also had a 20 percent higher risk of late stage at diagnosis compared with women with true negative findings, with delays in subsequent screening having a 0.3 percent increased risk of late stage at diagnosis per additional month of delay (p<0.001).

Researchers obtained screening data from 261,767 women presenting at a healthcare organization in Chicago, Illinois, US for bilateral mammograms between 2001 and 2010. Of the 741,150 mammograms, there were 650,232 true negative and 90,918 false positive results.

True negative results referred to negative, benign, or probably benign findings based on the Breast Imaging Reporting and Data System (BIRADS) with no cancer detected within 12 months of mammogram, while false positive referred to findings requiring additional imaging evaluation, suspicious abnormality, or highly suggestive of malignancy with no cancer detected within 12 months of mammogram.

Some previous studies demonstrated no difference in subsequent screening among women with false positive and true negative results, [Acta Oncol 2008;47:550-555] while others have demonstrated higher rescreening rates among women with prior false positive results. [Am J Med 2003;114:120-125]

“The conflicting results for international comparisons may be attributed to variations in screening practices such as screening intervals are shorter in the US than in Europe, greater emphasis on accuracy in Europe by double readings ... , and differences in national mammography programmes for Europe and US public and private screening providers,” said the researchers.

Researchers were unable to conclude if the women who did not undergo subsequent screening at these facilities sought out screening at other facilities or completely abandoned subsequent screening. The lack of information on insurance status was also a limitation as un- or underinsured women may delay or miss subsequent screening, particularly after false positive results, due to cost, they said.

“Women who experience a false positive mammogram result should be provided with more information about the continued benefits of mammography screening and encouraged to maintain adherence to screening mammography recommendations,” said the researchers.