Balancing harms and benefits of service mammography screening programs: a cohort study

Abstract

IntroductionThe use of screening mammography is still under debate within the medical community. The aim of this study is to define a balance sheet of benefits (breast cancer mortality reduction) and harms (overdiagnosis) for mammography screening programs.MethodsWe compared breast cancer incidence and mortality in two cohorts of women, defined as 'attenders' or 'non-attenders' on the basis of the individual attitudes towards screening, who were invited to the first round of the Florentine screening program. The effects of screening exposure on breast cancer incidence and mortality were evaluated by fitting Poisson regression models adjusted for age at entry, marital status and deprivation index. We performed a sensitivity analysis excluding 34 women not responding to the invitation with a breast cancer diagnosis in the following six months.ResultsIn total, we included 51,096 women aged 50 to 69 years invited at the first screening round (1991 to 1993) and followed-up for breast cancer incidence and mortality until 31 December 2007 and 31 December 2008, respectively The estimate of mortality reduction varies from 45% among 50 to 59 year-old women up to 51% among 60 to 69 year-old women. The estimate of overdiagnosis, according to the cumulative-incidence method, is an additional 10% of all breast cancer cases among 60 to 69 year-old women screened.ConclusionsComparing the breast cancer mortality and breast cancer incidence between attenders and non-attenders, we have determined that the overall cost to save one life corresponds to no more than one over-diagnosed tumor (from 0.6 to 1 depending on the selection criteria of the cohort), even if a residual self-selection bias cannot be excluded.

Effect of population breast screening on breast cancer mortality up to 2005 in England and Wales: an individual-level cohort study

“…A cohort study in Italy used the cumulative incidence method to investigate overdiagnosis in women aged 60–69 years at entry in the first round of the Florentine screening program. After 5–14 years follow-up, they found 5% overdiagnosis of invasive breast cancer alone and 10% overdiagnosis of invasive plus in situ breast cancer (1.10 (0.98–1.23); Puliti et al , 2012). Our estimate of overdiagnosis increases to 5% if follow-up is restricted to 7 years; however, this is less than the follow-up recommended (Independent UK Panel on Breast Cancer Screening, 2012), and the risk of overestimating overdiagnosis if follow-up is too short has been demonstrated (Duffy and Parmar, 2013).…”

Overdiagnosis among women attending a population‐based mammography screening program

“…Studies have shown large variation in the estimates of overdiagnosis, ranging from less than 1 to 54% . Estimates have been higher in studies based on aggregated data than in those based on individual data . This applied both for studies with and without DCIS included, and in studies related to invited or attending women.…”

Were Our Estimates of Overdiagnosis With Mammography Screening 
in the United States “Based on Faulty Science”?

“…In making these points, the critic may have missed the summary table of prior estimates of overdiagnosis we provided in our original supplemental online Appendix (repeated here in Table 3). The average overdiagnosis estimate in 12 studies from seven countries, including results from randomized controlled trials and retrospective general population studies, was 31.5%, 28% among studies in which the denominator was all cancer, and 24%, 33%, and 75% in 3 studies in which it was screen-detected cancers [18,[23][24][25][26][27][28][29][30][31][32][33]. Our best guess estimate of 31% is in the "middle of the pack.…”