Summary of the Evidence of Breast Cancer Service Screening Outcomes in Europe and First Estimate of the Benefit and Harm Balance Sheet

Abstract

Objectives To construct a European 'balance sheet' of key outcomes of population-based mammographic breast cancer screening, to inform policy-makers, stakeholders and invited women. Methods From the studies reviewed, the primary benefit of screening, breast cancer mortality reduction, was compared with the main harms, over-diagnosis and false-positive screening results (FPRs). Results Pooled estimates of breast cancer mortality reduction among invited women were 25% in incidence-based mortality studies and 31% in case-control studies (38% and 48% among women actually screened). Estimates of over-diagnosis ranged from 1% to 10% of the expected incidence in the absence of screening. The combined estimate of over-diagnosis for screened women, from European studies correctly adjusted for lead time and underlying trend, was 6.5%. For women undergoing 10 biennial screening tests, the estimated cumulative risk of a FPR followed by noninvasive assessment was 17%, and 3% having an invasive assessment. For every 1000 women screened biennially from age 50 -51 until age 68 -69 and followed up to age 79, an estimated seven to nine lives are saved, four cases are over-diagnosed, 170 women have at least one recall followed by non-invasive assessment with a negative result and 30 women have at least one recall followed by invasive procedures yielding a negative result. Conclusions The chance of saving a woman's life by population-based mammographic screening of appropriate quality is greater than that of over-diagnosis. Service screening in Europe achieves a mortality benefit at least as great as the randomized controlled trials. These outcomes should be communicated to women offered service screening in Europe.

Benefit-to-harm ratio of the Danish breast cancer screening programme

“…The EUROSCREEN estimates were based on joint data from the European service screening programmes available in 2012 1. For screened women, the reduction in breast cancer mortality was 38% in incidence‐based mortality studies and 48% in the case‐control, giving 7–9 prevented breast cancer deaths for 1,000 screened women.…”

“…In the Marmot report, the numbers were given for women aged 50 years and followed for 20 years 12. In the Two County Study for women aged 50–69 years at randomization,13 in the English data for women aged 45 and above,13 while both the Norwegian2 and the EUROSCREEN1 studies used data for women aged 50–79 years, as we did.…”

“…The estimates of breast cancer mortality reduction and overdiagnosis were extracted from our previous studies, which used the difference‐in‐differences method based on four cohorts with individual follow‐up data 3, 4, 5. The methodology presented by the EUROSCREEN group was used to estimate the number of breast cancer deaths prevented and the number of overdiagnosed cases 1. As the EUROSCREEN group estimation is based on cumulative rates for age 50 to 79, the results of our present study will differ from our previously published estimates on number of breast cancer deaths prevented4 and on number of overdiagnosed cases5 using other methods.…”

“…In 2012, the EUROSCREEN group estimated that for every 1,000 women screened, 7 to 9 breast cancer death would be prevented, and 4 cases would be overdiagnosed, giving a ratio between 1.8 and 2.3 1. Using the same methodology, Hofvind et al .…”

To screen or not to screen

“…4 Conversely, the European Screening Network (EUROSCREEN) working group suggests that 7 to 9 lives could be saved by a biennial screening of approximately 1000 women, a nearly 20-fold difference. 5 The controversies, and charges of underinflation or overinflation, are even more dramatic for estimates of breast cancer overdiagnosis. The numbers "are all over the place," Dr. Smith says, varying from zero to greater than one-half of all cancers diagnosed via screening, depending on the methodology used.…”