False-positive mammography results occur in 14% of women at first screening and for 8% at subsequent examinations. With adherence to current guidelines in the United States, a woman starting biennial screening at age 50 years and stopping at age 74 years will undergo 12 screening mammography examinations in her lifetime. It has been estimated that the probability of at least 1 false-positive recall after 10 screening examinations ranges from 29% to 77% and from 8% to 9% for benign biopsy findings.
Few studies have estimated the cumulative probability of false-positive mammography results after repeated screening in U.S. women. Limited data suggest that biennial screening mammography reduces false-positive results and biopsy recommendations but may also delay cancer diagnosis.
This prospective cohort study compared the cumulative probability after 10 years of annual and biennial screening mammography of false-positive recalls and biopsy recommendations in a population of women who started screening at age 40 to 59 years. Data were obtained from 7 mammography registries in the National Cancer Institute–funded Breast Cancer Surveillance Consortium. The study cohort included 169,456 women who underwent first screening mammography between 1994 and 2006, and 4492 women with a diagnosis of incident invasive breast cancer between 1996 and 2006. The probabilities for false-positive recalls and biopsy recommendations stage distribution of incident breast cancer were stratified by age at diagnosis (age, 40–49 and 50–59 years).
The probability of a mammogram leading to false-positive recall was 16.3% for first and 9.6% for subsequent mammograms. With respect to the biopsy recommendations, the probability of a false-positive result was 2.5% for the first and 1.0% for subsequent examinations. When comparison mammograms were available, the odds of a false-positive recall were halved; the adjusted odds ratio was 0.50, with a 95% confidence interval (CI) of 0.45 to 0.56. Among women starting screening at age 40 years, the cumulative probability of a false-positive recall after 10 years with annual screening was 61.3% (95% CI, 59.4%–63.1%); with biennial screening, the probability decreased to 41.6% (95% CI, 40.6%–42.5%). When screening started at age 40 years, cumulative probability of a false-positive biopsy recommendation was 7.0% (95% CI, 6.1%–7.8%) with annual screening; with biennial screening, the probability decreased to 4.8% (95% CI, 4.4%–5.2%). When screening began at age 50 years, probability estimates were similar. There was a small statistically insignificant increase in the proportion of late-stage cancers with biennial compared with annual screening; absolute increases of incident breast cancer were 3.3 percentage points (95% CI, −1.1 to 7.8 percentage points) for women aged 40 to 49 years and 2.3 percentage points (95% CI, −1.0 to 5.7 percentage points) for women aged 50 to 59 years. Limitations of this study included small numbers of women screened during the entire 10-year study period, the small population of women who developed cancer, lack of information on the characteristics of the interpreting radiologists, and the use of film-screen mammograms for most analyses.
These findings show that after 10 years of annual screening, the majority of women will receive at least 1 false-positive recall, and 6% to 8% will have a false-positive biopsy recommendation. Biennial screening appears to reduce false-positive results but may be associated with a small absolute increase in the diagnosis of late-stage breast cancer.