Roughly 1 in 5 women who completed 10 biennial breast cancer screenings received a false-positive result in a population-based study out of Norway.

About 1 in 20 patients had an invasive procedure due to a false-positive result. These findings were published in Cancer.

For this study, researchers retrospectively evaluated data from 421,545 women who participated in BreastScreen Norway, a population-based screening program that includes biennial mammography.

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By December 20, 2019, there were 18,203 patients who had undergone 10 screenings over 20 years. The mean age at the tenth screening was 68.5 years (range, 66-71 years).

Patients were classified as having a false-positive screening result if they were called for further assessment after mammography due to abnormal findings and were not diagnosed with ductal carcinoma in situ or invasive breast cancer within 180 days of the screening exam.

A false-positive result was seen in 10.5% of patients, 2 or more false positives were seen in 0.8%, and 3.1% of patients underwent an invasive procedure as a result of a false positive. Invasive procedures included fine-needle aspiration cytology, core-needle biopsy, and open biopsy.

After 10 screening rounds, the cumulative risk of receiving a first false-positive result was 18.04%, and the risk of undergoing an invasive procedure as a result of a first false-positive was 5.01%.

The researchers noted that these numbers differ from numbers observed in US studies, which suggest a higher cumulative risk of false positives (42%-59%) and invasive procedures after false-positive results (6%-19%).


Tsuruda KM, Larsen M, Román M, Hofvind S. Cumulative risk of a false-positive screening result: A retrospective cohort study using empirical data from 10 biennial screening rounds in BreastScreen Norway. Cancer. Published online December 21, 2021. doi:10.1002/cncr.34078