False-Positive Results in the Randomized Controlled Trial of Mammographic Screening from Age 40 (“Age” Trial)

Abstract

Background False-positive recall is a recognised disadvantage of mammographic breast screening and the rate of such recalls may be higher in younger women, potentially limiting the value of screening below age 50. Methods Attendance and screening outcome data for 53 884 women in the intervention arm of the UK Age trial were analysed to report observed false-positive recall rates during 13 years of trial fieldwork. The Age trial was a randomised controlled trial of the effect of mammographic screening from age 40 on breast cancer mortality, conducted in 23 NHS Screening centres between 1991 and 2004. Women randomised to the intervention arm were offered annual invitation to mammography from age 40/41 to age 48. Results Overall, 7893 women (14.6% of women the intervention arm and 18.1% of women attending at least one routine screen) experienced one or more false-positive screen during the trial. The rates of false-positive mammography at first and subsequent routine screens were 4.9% and 3.2%, respectively. The cumulative false-positive rate over seven screens was 20.5%. Eighty-nine percent of women who had a false-positive recall at their previous screen attended their next invitation to routine screening. Conclusions Rates of false-positive recall in the Age trial were comparable with the national screening programme, however, the positive predictive value of referral was lower. Experiencing a false-positive screen did not appear to lessen the likelihood of re-attendance in the trial. Impact The question of greatly increased false-positive rates in this age group and of their compromising re-attendance is refuted by the findings of this study.

Is the false-positive rate in mammography in North America too high?

“…20 From these data, it can be seen that the average FP rate associated with screening mammography in North America can be estimated to fall between approximately 6% and 10%. The North American rates contrast greatly with those observed in Europe, whereby the average FP rate among the first and subsequent screens in the Netherlands and the UK are only 2% 23 and 4.9%, 24 respectively. In accordance with European regulations, these jurisdictions are in compliance with the mandate for limiting the mammography FP rate to below 5%.…”

Screening methods(clinical breast examination and mammography) to detect breast cancer in women aged 40–49 years

“…Results from the age trial do not suggest that a new policy for inviting breast screening from age 47 will result in large increase in false positives and will prevent women from re-attendance. [14]…”

“…Whether screening should be implemented in this age group is a separate issue, but the question of greatly increased false-positive rates in this age group and of their compromising re-attendance is refuted by the findings of this study and should be taken into account when determining screening policy. [14]…”

Breast Cancer Screening

“…In the United States, the false positive rate is estimated to be 10% of women screened with mammography. 79,80 Table 1 shows estimates that out of 10,000 women screened annually with mammography for 10 years, 4,970 to 6,130 women will receive at least one false positive result in 10 years. It is estimated that 700 to 980 women who receive false positives undergo unnecessary biopsies.…”