Overdiagnosis by mammographic screening for breast cancer studied in birth cohorts in The Netherlands

Abstract

A drawback of early detection of breast cancer through mammographic screening is the diagnosis of breast cancers that would never have become clinically detected. This phenomenon, called overdiagnosis, is ideally quantified from the breast cancer incidence of screened and unscreened cohorts of women with follow-up until death. Such cohorts do not exist, requiring other methods to estimate overdiagnosis. We are the first to quantify overdiagnosis from invasive breast cancer and ductal carcinoma in situ (DCIS) in birth cohorts using an age-period-cohort -model (APC-model) including variables for the initial and subsequent screening rounds and a 5-year period after leaving screening. Data on the female population and breast cancer incidence were obtained from Statistics Netherlands, "Stichting Medische registratie" and the Dutch Cancer Registry for women aged 0-99 years. Data on screening participation was obtained from the five regional screening organizations. Overdiagnosis was calculated from the excess breast cancer incidence in the screened group divided by the breast cancer incidence in presence of screening for women aged 20-99 years (population perspective) and for women in the screened-age range (individual perspective). Overdiagnosis of invasive breast cancer was 11% from the population perspective and 17% from the invited women perspective in birth cohorts screened from age 49 to 74. For invasive breast cancer and DCIS together, overdiagnosis was 14% from population perspective and 22% from invited women perspective. A major strength of an APC-model including the different phases of screening is that it allows to estimate overdiagnosis in birth cohorts, thereby preventing overestimation.

A modelling study to evaluate the costs and effects of lowering the starting age of population breast cancer screening

“…According to a comprehensive review on European breast cancer screening programmes this overdiagnosis accounts on average for 6.5% of all screen detected breast cancers [1]. A recent analysis estimated 11% overdiagnosed tumours in the Dutch breast cancer screening programme [44]. With the introduction of national breast cancer screening programmes, the rate of detection of large tumours decreased in favour of small tumours.…”

Is the incidence of advanced‐stage breast cancer affected by whether women attend a steady‐state screening program?

“…27 The likely extent of overdiagnosis is unclear, but previous studies have given estimates that range from 0% to 52%. 12,[40][41][42] The increase in early stage breast cancer might also be caused by the higher detection ability of digital mammography during the latter study period. If present, one would expect overdiagnosis to cause a higher overall incidence in screened women compared with nonscreened women, yet rates were similar throughout the study period (389 and 403 per 100,000, respectively; p 5 0.619).…”

Mortality of women with ductal carcinoma in situ of the breast: a population-based study from the Girona province, Spain (1994–2013)

“…With the improvements in radiological and pathological assessment there has been a decrease in the number of unrecognized invasive BC infiltrations-linked to especially poor survival prognosis-at DCIS diagnosis. In addition, the extended implementation of screening programs has been related to an increment in over diagnosis [29,30]-i.e., the diagnosis of a lesion that will never cause symptoms or death during a patient's lifetime. This is magnified if adherence to screening programs is high, as reported in a meta-analysis of intention-to-treat randomized control trials conducted by Jacklyn et al [31].…”

“…The lower risk of all-cause death among women diagnosed through screening compared to the general population, yet not significant, further supports this finding. The magnitude of the risk estimate and its lack of significance could be partially attributed to the associated risk of physical, psychological and financial harm due to overdiagnosis and treatment that has been associated with mammography use [30,35].…”