The cumulative risk of false-positive results in the Norwegian Breast Cancer Screening Program: updated results

Abstract

Background: Some false-positive results are inevitable in mammographic screening, but the impact of false-positive findings on the program and the participants is a disadvantage of screening. The objective of the current study was to estimate the cumulative risk of a false-positive result over 10 biennial screening examinations and the cumulative risk of undergoing an invasive procedure with a benign outcome in women screened between the ages of 50 years to 69 years.

Methods: A retrospective cohort study was performed in 231,310 women aged 50 years to 51 years at the time of first mammography screening who underwent 715,311 screening mammograms in the Norwegian Breast Cancer Screening Program from 1996 through 2010. Generalized linear mixed models were used to estimate the probability of a false-positive screening result and to compute the cumulative false-positive risk for up to 10 biennial screening examinations.

Results: The cumulative false-positive risk after 20 years of biennial screening for women who initiated screening aged 50 years to 51 years was 20.0% (95% confidence interval [95% CI], 19.7%-20.4%). The cumulative risk of undergoing an invasive procedure with a benign outcome for the same group of women was 4.1% (95% CI, 3.9%-4.3%). The cumulative risk of undergoing a fine-needle aspiration cytology, core needle biopsy, or open biopsy with a benign outcome was 1.4% (95% CI, 1.3%-1.5%), 2.0% (95% CI, 1.9%-2.1%), and 0.16% (95% CI, 0.13%-0.19%), respectively.

Conclusions: One in every 5 women will be recalled for further assessment with a negative outcome if they attend biennial mammographic screening between ages 50 years to 69 years. The risk of an invasive procedure with a benign outcome is approximately 4%. It is important to communicate the existence and extent of this risk to the target group and to reduce to a minimum the waiting times between screening and further assessment.

Keywords: breast neoplasms; false-positive results; female; mammography; mass screening.