Impact of intermediate mammography assessment on the likelihood of false-positive results in breast cancer screening programmes.

OBJECTIVES: Breast cancer screening is offered to 100% of the target population in Spain and intermediate mammograms (IMs) are sometimes indicated. This study was aimed at analysing the frequency of IMs, the factors determining their recommendation, and their impact on the risk of false-positive results and the detection rate.
METHODS: Data from 3,471,307 mammograms from Spanish breast cancer screening programmes were included.
RESULTS: 3.36% of the mammograms were IMs. The factors associated with the use of IMs were age, initial screening, previous invasive tests, a familial history of breast cancer and use of hormone replacement therapy. In screening episodes with an IM, the probability of a false-positive result was 13.74% (95% CI: 13.43-14.05), almost double that in episodes without IMs (6.02%, 95% CI 5.99-6.05). In young women with previous invasive procedures, a familial history of breast cancer or hormone replacement therapy use who were undergoing their initial screen, this probability was lower when IMs were performed. IMs always increased the detection rate.
CONCLUSIONS: The factors prompting IMs should be characterised so that radiologists can systematise their recommendations according to the presence of the factors maximising the benefits and minimising the adverse effects of this procedure. KEY POINTS: Intermediate mammograms in breast screening offer potential benefits but also disadvantages. Intermediate mammograms increase the false-positive rate except in specific groups. Intermediate mammograms reduce the false-positive rate in younger women and initial screens. Intermediate mammograms also reduce false-positive results in women with personal risk factors. Intermediate mammograms increase cancer detection mainly in women without risk factors.