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Buschmann L, Wellmann I, Bonberg N, Wellmann J, Hense HW, Karch A, Minnerup H. Isolating the effect of confounding from the observed survival benefit of screening participants - a methodological approach illustrated by data from the German mammography screening programme. BMC Med 2024; 22:43. [PMID: 38287392 PMCID: PMC10826012 DOI: 10.1186/s12916-024-03258-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/11/2023] [Accepted: 01/15/2024] [Indexed: 01/31/2024] Open
Abstract
BACKGROUND Mammography screening programmes (MSP) aim to reduce breast cancer mortality by shifting diagnoses to earlier stages. However, it is difficult to evaluate the effectiveness of current MSP because analyses can only rely on observational data, comparing women who participate in screening with women who do not. These comparisons are subject to several biases: one of the most important is self-selection into the MSP, which introduces confounding and is difficult to control for. Here, we propose an approach to quantify confounding based on breast cancer survival analyses using readily available routine data sources. METHODS Using data from the Cancer Registry of North Rhine-Westphalia, Germany, we estimate the relative contribution of confounding to the observed survival benefit of participants of the German MSP. This is accomplished by comparing non-participants, participants with screen-detected and participants with interval breast cancers for the endpoints "death from breast cancer" and "death from all causes other than breast cancer" - the latter being assumed to be unrelated to any MSP effect. By using different contrasts, we eliminate the effects of stage shift, lead and length time bias. The association of breast cancer detection mode with survival is analysed using Cox models in 68,230 women, aged 50-69 years, with breast cancer diagnosed in 2006-2014 and followed up until 2018. RESULTS The hazard of dying from breast cancer was lower in participants with screen-detected cancer than in non-participants (HR = 0.21, 95% CI: 0.20-0.22), but biased by lead and length time bias, and confounding. When comparing participants with interval cancers and non-participants, the survival advantage was considerably smaller (HR = 0.62, 95% CI: 0.58-0.66), due to the elimination of stage shift and lead time bias. Finally, considering only mortality from causes other than breast cancer in the latter comparison, length time bias was minimised, but a survival advantage was still present (HR = 0.63, 95% CI: 0.56-0.70), which we attribute to confounding. CONCLUSIONS This study shows that, in addition to stage shift, lead and length time bias, confounding is an essential component when comparing the survival of MSP participants and non-participants. We further show that the confounding effect can be quantified without explicit knowledge of potential confounders by using a negative control outcome.
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Affiliation(s)
- Laura Buschmann
- Institute of Epidemiology and Social Medicine, University of Münster, Münster, Germany.
| | - Ina Wellmann
- Cancer Registry of North Rhine-Westphalia, Bochum, Germany
| | - Nadine Bonberg
- Institute of Epidemiology and Social Medicine, University of Münster, Münster, Germany
| | - Jürgen Wellmann
- Institute of Epidemiology and Social Medicine, University of Münster, Münster, Germany
| | - Hans-Werner Hense
- Institute of Epidemiology and Social Medicine, University of Münster, Münster, Germany
| | - André Karch
- Institute of Epidemiology and Social Medicine, University of Münster, Münster, Germany
| | - Heike Minnerup
- Institute of Epidemiology and Social Medicine, University of Münster, Münster, Germany
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De Troeyer K, Silversmit G, Rosskamp M, Truyen I, Van Herck K, Goossens MM, Martens P, Kellen E, Hendrickx E, Rummens E, De Smet F, Broeders M, Verdoodt F, De Schutter H. The effect of the Flemish breast cancer screening program on breast cancer-specific mortality: A case-referent study. Cancer Epidemiol 2023; 82:102320. [PMID: 36608495 DOI: 10.1016/j.canep.2022.102320] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2022] [Revised: 11/21/2022] [Accepted: 12/19/2022] [Indexed: 01/06/2023]
Abstract
BACKGROUND Breast cancer screening programs were introduced in many countries worldwide following randomized controlled trials in the 1980s showing a reduction in breast cancer-specific mortality. However, their effectiveness remains debated and estimates vary. A breast cancer screening program was introduced in 2001 in Flanders, Belgium where high levels of opportunistic screening practices are observed. The effectiveness of this program was estimated by measuring its effect on breast cancer-specific mortality. METHODS We performed a case-referent study to investigate the effect of participation in the Flemish population-based mammography screening program (PMSP) on breast cancer-specific mortality from 2005 to 2017. A multiple logistic regression model assessed the association between breast cancer-specific death and screening program participation status in the four years prior to (pseudo)diagnosis (yes/no), with adjustment for potential confounders (individual socio-economic position and calendar year of diagnosis) and stratified for age. In addition, we performed different sensitivity analyses. RESULTS We identified 1571 cases and randomly selected 6284 referents. After adjustment, women who participated in PMSP had a 51 % lower risk of breast cancer-specific mortality compared to those who did not (adjusted odds ratio [aOR] =0.49, 95 % CI: 0.44-0.55). Sensitivity analyses did not markedly change the estimated associations. Correction for self-selection bias reduced the effect size, but the estimate remained significant. CONCLUSION Our results indicate that in a context of high opportunistic screening rates, participation in breast cancer screening program substantially reduces breast cancer-specific mortality. For policy, these results should be balanced against the potential harms of screening, including overdiagnosis and overtreatment.
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Affiliation(s)
- Katrien De Troeyer
- Belgian Cancer Registry, 1210 Brussels, Belgium; Family Medicine and Population Health, Department of Epidemiology and Social Medicine, University of Antwerp, 2000 Antwerp, Belgium
| | | | | | - Inge Truyen
- Belgian Cancer Registry, 1210 Brussels, Belgium
| | | | - Mathijs Michiel Goossens
- Centre for Cancer Detection, 8000 Bruges, Belgium; Vrije Universiteit Brussel, 1090 Brussels, Belgium
| | | | - Eliane Kellen
- Centre for Cancer Detection, 8000 Bruges, Belgium; University Hospital Leuven, Campus Sint Rafael, 3000 Leuven, Belgium
| | - Erik Hendrickx
- Agency for Care and Health, Flemish Government, 1030 Brussels, Belgium
| | - Elise Rummens
- Christian Health Insurance Fund, 1031 Brussels, Belgium
| | - Frank De Smet
- Christian Health Insurance Fund, 1031 Brussels, Belgium; Department of Public Health and Primary Care, Environment and Health, KU Leuven, 3000 Leuven, Belgium
| | - Mireille Broeders
- Radboud University Medical Center, Radboud Institute for Health Sciences, Nijmegen, the Netherlands
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Impact of mammographic screening and advanced cancer definition on the percentage of advanced-stage cancers in a steady-state breast screening programme in the Netherlands. Br J Cancer 2020; 123:1191-1197. [PMID: 32641863 PMCID: PMC7524754 DOI: 10.1038/s41416-020-0968-6] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2020] [Revised: 06/09/2020] [Accepted: 06/18/2020] [Indexed: 11/13/2022] Open
Abstract
Background To estimate the percentages of advanced-stage breast cancers (BCs) detected during the course of a steady-state screening programme when using different definitions of advanced BC. Methods Data of women aged 49–74 years, diagnosed with BC in 2006–2015, were selected from the Netherlands Cancer Registry and linked to the screening registry. BCs were classified as screen-detected, interval or non-screened. Three definitions of advanced BC were used for comparison: TNM stage (III–IV), NM stage (N+ and/or M+) and T size (invasive tumour ≥15 mm). Analyses were performed assuming a 10% overdiagnosis rate. In sensitivity analyses, this assumption varied from 0 to 30%. Results We included 46,734 screen-detected, 17,362 interval and 24,189 non-screened BCs. By TNM stage, 4.9% of screen-detected BCs were advanced, compared with 19.4% and 22.8% of interval and non-screened BCs, respectively (p < 0.001). Applying the other definitions led to higher percentages of advanced BC being detected. Depending on the definition interval, non-screened BCs had a 2–5-times risk of being advanced. Conclusion Irrespective of the definition, screen-detected BCs were less frequently in the advanced stage. These findings provide evidence of a stage shift to early detection and support the potential of mammographic screening to reduce treatment-related burdens and the mortality associated with BC.
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Lousdal ML, Lash TL, Flanders WD, Brookhart MA, Kristiansen IS, Kalager M, Støvring H. Negative controls to detect uncontrolled confounding in observational studies of mammographic screening comparing participants and non-participants. Int J Epidemiol 2020; 49:1032-1042. [PMID: 32211885 PMCID: PMC7394947 DOI: 10.1093/ije/dyaa029] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/03/2020] [Indexed: 11/24/2022] Open
Abstract
BACKGROUND When comparing mammography-screening participants and non-participants, estimates of reduction in breast-cancer mortality may be biased by poor baseline comparability. We used negative controls to detect uncontrolled confounding. METHODS We designed a closed cohort of Danish women invited to a mammography-screening programme at age 50-52 years in Copenhagen or Funen from 1991 through 2001. We included women with a normal screening result in their first-invitation round. Based on their second-invitation round, women were divided into participants and non-participants and followed until death, emigration or 31 December 2014, whichever came first. We estimated hazard ratios (HRs) of death from breast cancer, causes other than breast cancer and external causes. We added dental-care participation as an exposure to test for an independent association with breast-cancer mortality. We adjusted for civil status, parity, age at first birth, educational attainment, income and hormone use. RESULTS Screening participants had a lower hazard of breast-cancer death [HR 0.47, 95% confidence interval (CI) 0.32, 0.69] compared with non-participants. Participants also had a lower hazard of death from other causes (HR 0.43, 95% CI 0.39, 0.46) and external causes (HR 0.35, 95% CI 0.23, 0.54). Reductions persisted after covariate adjustment. Dental-care participants had a lower hazard of breast-cancer death (HR 0.75, 95% CI 0.56, 1.01), irrespective of screening participation. CONCLUSIONS Negative-control associations indicated residual uncontrolled confounding when comparing breast-cancer mortality among screening participants and non-participants.
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Affiliation(s)
| | - Timothy L Lash
- Department of Epidemiology, Rollins School of Public Health, Emory University, Atlanta, GA, USA
- Winship Cancer Institute, Emory University, Atlanta, GA, USA
| | - W Dana Flanders
- Department of Epidemiology, Rollins School of Public Health, Emory University, Atlanta, GA, USA
- Winship Cancer Institute, Emory University, Atlanta, GA, USA
| | - M Alan Brookhart
- Department of Population Health Sciences, Duke University, Durham, NC, USA
| | | | - Mette Kalager
- Department of Health Management and Health Economics, Oslo University, Oslo, Norway
- Clinical effectiveness research group, Oslo University Hospital, Oslo, Norway
| | - Henrik Støvring
- Department of Public Health, Aarhus University, Aarhus, Denmark
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de Munck L, Fracheboud J, de Bock GH, den Heeten GJ, Siesling S, Broeders MJM. Is the incidence of advanced-stage breast cancer affected by whether women attend a steady-state screening program? Int J Cancer 2018; 143:842-850. [PMID: 29574967 DOI: 10.1002/ijc.31388] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2017] [Revised: 02/26/2018] [Accepted: 02/28/2018] [Indexed: 11/05/2022]
Abstract
In this cross-sectional population-based study, we assessed the incidence of advanced breast cancer based on screening attendance. Women from the Netherlands Cancer Registry were included if aged ≥49 years and diagnosed with breast cancer between 2006 and 2011, and data were linked with the screening program. Cancers were defined as screen-related (diagnosed <24 months after screening) or nonscreened (all other breast cancers). Two cut-offs were used to define advanced breast cancer: TNM-stage (III-IV vs 0-I-II) and T-stage alone (≥15 mm vs <15 mm or DCIS). The incidence rates were adjusted for age and logistic regression was used to compare groups. Of the 72,612 included women diagnosed with breast cancer, 44,246 (61%) had screen-related breast cancer. By TNM stage, advanced cancer was almost three times as likely to be at an advanced TNM stage in the nonscreened group compared with the screen-related group (38 and 94 per 100,000, respectively; OR: 2.86, 95%CI: 2.72-3.00). By T-stage, the incidence of advanced cancer was higher overall, and in nonscreened women was significantly higher than in screened women (210 and 169 per 100,000; OR: 1.85, 95%CI: 1.78-1.93). Data on actual screening attendance showed that the incidence of advanced breast cancer was significantly higher in nonscreened women than in screened women, supporting the expectation that screening would cause a stage shift to early detection. Despite critical evaluations of breast cancer screening programs, our data show that breast cancer screening is a valuable tool that can reduce the disease burden in women.
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Affiliation(s)
- Linda de Munck
- Department of Research, Netherlands Comprehensive Cancer Organisation, Utrecht, The Netherlands.,Department of Epidemiology, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands
| | - Jacques Fracheboud
- Department of Public Health, Erasmus MC, University Medical Center Rotterdam, Rotterdam, The Netherlands
| | - Geertruida H de Bock
- Department of Epidemiology, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands
| | - Gerard J den Heeten
- Dutch Reference Centre for Screening, Nijmegen, The Netherlands.,Department of Radiology, Academic Medical Centre Amsterdam, Amsterdam, The Netherlands
| | - Sabine Siesling
- Department of Research, Netherlands Comprehensive Cancer Organisation, Utrecht, The Netherlands.,Department of Health Technology & Services Research, MIRA Institute for Biomedical Technology and Technical Medicine, University of Twente, Enschede, The Netherlands
| | - Mireille J M Broeders
- Dutch Reference Centre for Screening, Nijmegen, The Netherlands.,Radboud Institute for Health Sciences, Radboud University Medical Center, Nijmegen, The Netherlands
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Autier P, Boniol M. Mammography screening: A major issue in medicine. Eur J Cancer 2017; 90:34-62. [PMID: 29272783 DOI: 10.1016/j.ejca.2017.11.002] [Citation(s) in RCA: 81] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2017] [Accepted: 11/03/2017] [Indexed: 01/20/2023]
Abstract
Breast cancer mortality is declining in most high-income countries. The role of mammography screening in these declines is much debated. Screening impacts cancer mortality through decreasing the incidence of number of advanced cancers with poor prognosis, while therapies and patient management impact cancer mortality through decreasing the fatality of cancers. The effectiveness of cancer screening is the ability of a screening method to curb the incidence of advanced cancers in populations. Methods for evaluating cancer screening effectiveness are based on the monitoring of age-adjusted incidence rates of advanced cancers that should decrease after the introduction of screening. Likewise, cancer-specific mortality rates should decline more rapidly in areas with screening than in areas without or with lower levels of screening but where patient management is similar. These two criteria have provided evidence that screening for colorectal and cervical cancer contributes to decreasing the mortality associated with these two cancers. In contrast, screening for neuroblastoma in children was discontinued in the early 2000s because these two criteria were not met. In addition, overdiagnosis - i.e. the detection of non-progressing occult neuroblastoma that would not have been life-threatening during the subject's lifetime - is a major undesirable consequence of screening. Accumulating epidemiological data show that in populations where mammography screening has been widespread for a long time, there has been no or only a modest decline in the incidence of advanced cancers, including that of de novo metastatic (stage IV) cancers at diagnosis. Moreover, breast cancer mortality reductions are similar in areas with early introduction and high penetration of screening and in areas with late introduction and low penetration of screening. Overdiagnosis is commonplace, representing 20% or more of all breast cancers among women invited to screening and 30-50% of screen-detected cancers. Overdiagnosis leads to overtreatment and inflicts considerable physical, psychological and economic harm on many women. Overdiagnosis has also exerted considerable disruptive effects on the interpretation of clinical outcomes expressed in percentages (instead of rates) or as overall survival (instead of mortality rates or stage-specific survival). Rates of radical mastectomies have not decreased following the introduction of screening and keep rising in some countries (e.g. the United States of America (USA)). Hence, the epidemiological picture of mammography screening closely resembles that of screening for neuroblastoma. Reappraisals of Swedish mammography trials demonstrate that the design and statistical analysis of these trials were different from those of all trials on screening for cancers other than breast cancer. We found compelling indications that these trials overestimated reductions in breast cancer mortality associated with screening, in part because of the statistical analyses themselves, in part because of improved therapies and underreporting of breast cancer as the underlying cause of death in screening groups. In this regard, Swedish trials should publish the stage-specific breast cancer mortality rates for the screening and control groups separately. Results of the Greater New York Health Insurance Plan trial are biased because of the underreporting of breast cancer cases and deaths that occurred in women who did not participate in screening. After 17 years of follow-up, the United Kingdom (UK) Age Trial showed no benefit from mammography screening starting at age 39-41. Until around 2005, most proponents of breast screening backed the monitoring of changes in advanced cancer incidence and comparative studies on breast cancer mortality for the evaluation of breast screening effectiveness. However, in an attempt to mitigate the contradictions between results of mammography trials and population data, breast-screening proponents have elected to change the criteria for the evaluation of cancer screening effectiveness, giving precedence to incidence-based mortality (IBM) and case-control studies. But practically all IBM studies on mammography screening have a strong ecological component in their design. The two IBM studies done in Norway that meet all methodological requirements do not document significant reductions in breast cancer mortality associated with mammography screening. Because of their propensity to exaggerate the health benefits of screening, case-control studies may demonstrate that mammography screening could reduce the risk of death from diseases other than breast cancer. Numerous statistical model approaches have been conducted for estimating the contributions of screening and of patient management to reductions in breast cancer mortality. Unverified assumptions are needed for running these models. For instance, many models assume that if screening had not occurred, the majority of screen-detected asymptomatic cancers would have progressed to symptomatic advanced cancers. This assumption is not grounded in evidence because a large proportion of screen-detected breast cancers represent overdiagnosis and hence non-progressing tumours. The accumulation of population data in well-screened populations diminishes the relevance of model approaches. The comparison of the performance of different screening modalities - e.g. mammography, digital mammography, ultrasonography, magnetic resonance imaging (MRI), three-dimensional tomosynthesis (TDT) - concentrates on detection rates, which is the ability of a technique to detect more cancers than other techniques. However, a greater detection rate tells little about the capacity to prevent interval and advanced cancers and could just reflect additional overdiagnosis. Studies based on the incidence of advanced cancers and on the evaluation of overdiagnosis should be conducted before marketing new breast-imaging technologies. Women at high risk of breast cancer (i.e. 30% lifetime risk and more), such as women with BRCA1/2 mutations, require a close breast surveillance. MRI is the preferred imaging method until more radical risk-reduction options are eventually adopted. For women with an intermediate risk of breast cancer (i.e. 10-29% lifetime risk), including women with extremely dense breast at mammography, there is no evidence that more frequent mammography screening or screening with other modalities actually reduces the risk of breast cancer death. A plethora of epidemiological data shows that, since 1985, progress in the management of breast cancer patients has led to marked reductions in stage-specific breast cancer mortality, even for patients with disseminated disease (i.e. stage IV cancer) at diagnosis. In contrast, the epidemiological data point to a marginal contribution of mammography screening in the decline in breast cancer mortality. Moreover, the more effective the treatments, the less favourable are the harm-benefit balance of screening mammography. New, effective methods for breast screening are needed, as well as research on risk-based screening strategies.
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Affiliation(s)
- Philippe Autier
- University of Strathclyde Institute of Global Public Health at IPRI, International Prevention Research Institute, Espace Européen, Building G, Allée Claude Debussy, 69130 Ecully Lyon, France; International Prevention Research Institute (iPRI), 95 Cours Lafayette, 69006 Lyon, France.
| | - Mathieu Boniol
- University of Strathclyde Institute of Global Public Health at IPRI, International Prevention Research Institute, Espace Européen, Building G, Allée Claude Debussy, 69130 Ecully Lyon, France; International Prevention Research Institute (iPRI), 95 Cours Lafayette, 69006 Lyon, France
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Ripping TM, Ten Haaf K, Verbeek ALM, van Ravesteyn NT, Broeders MJM. Quantifying Overdiagnosis in Cancer Screening: A Systematic Review to Evaluate the Methodology. J Natl Cancer Inst 2017; 109:3845953. [PMID: 29117353 DOI: 10.1093/jnci/djx060] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2016] [Accepted: 03/10/2017] [Indexed: 12/21/2022] Open
Abstract
Background Overdiagnosis is the main harm of cancer screening programs but is difficult to quantify. This review aims to evaluate existing approaches to estimate the magnitude of overdiagnosis in cancer screening in order to gain insight into the strengths and limitations of these approaches and to provide researchers with guidance to obtain reliable estimates of overdiagnosis in cancer screening. Methods A systematic review was done of primary research studies in PubMed that were published before January 1, 2016, and quantified overdiagnosis in breast cancer screening. The studies meeting inclusion criteria were then categorized by their methods to adjust for lead time and to obtain an unscreened reference population. For each approach, we provide an overview of the data required, assumptions made, limitations, and strengths. Results A total of 442 studies were identified in the initial search. Forty studies met the inclusion criteria for the qualitative review. We grouped the approaches to adjust for lead time in two main categories: the lead time approach and the excess incidence approach. The lead time approach was further subdivided into the mean lead time approach, lead time distribution approach, and natural history modeling. The excess incidence approach was subdivided into the cumulative incidence approach and early vs late-stage cancer approach. The approaches used to obtain an unscreened reference population were grouped into the following categories: control group of a randomized controlled trial, nonattenders, control region, extrapolation of a prescreening trend, uninvited groups, adjustment for the effect of screening, and natural history modeling. Conclusions Each approach to adjust for lead time and obtain an unscreened reference population has its own strengths and limitations, which should be taken into consideration when estimating overdiagnosis.
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Affiliation(s)
- Theodora M Ripping
- Affiliations of authors: Radboud Institute for Health Sciences, Radboud University Medical Center, Nijmegen, the Netherlands (TMR, ALMV, MJMB); Department of Public Health, Erasmus MC, University Medical Centre, Rotterdam, the Netherlands (KtH, NTvR); Dutch Reference Centre for Screening, Nijmegen, the Netherlands (MJMB)
| | - Kevin Ten Haaf
- Affiliations of authors: Radboud Institute for Health Sciences, Radboud University Medical Center, Nijmegen, the Netherlands (TMR, ALMV, MJMB); Department of Public Health, Erasmus MC, University Medical Centre, Rotterdam, the Netherlands (KtH, NTvR); Dutch Reference Centre for Screening, Nijmegen, the Netherlands (MJMB)
| | - André L M Verbeek
- Affiliations of authors: Radboud Institute for Health Sciences, Radboud University Medical Center, Nijmegen, the Netherlands (TMR, ALMV, MJMB); Department of Public Health, Erasmus MC, University Medical Centre, Rotterdam, the Netherlands (KtH, NTvR); Dutch Reference Centre for Screening, Nijmegen, the Netherlands (MJMB)
| | - Nicolien T van Ravesteyn
- Affiliations of authors: Radboud Institute for Health Sciences, Radboud University Medical Center, Nijmegen, the Netherlands (TMR, ALMV, MJMB); Department of Public Health, Erasmus MC, University Medical Centre, Rotterdam, the Netherlands (KtH, NTvR); Dutch Reference Centre for Screening, Nijmegen, the Netherlands (MJMB)
| | - Mireille J M Broeders
- Affiliations of authors: Radboud Institute for Health Sciences, Radboud University Medical Center, Nijmegen, the Netherlands (TMR, ALMV, MJMB); Department of Public Health, Erasmus MC, University Medical Centre, Rotterdam, the Netherlands (KtH, NTvR); Dutch Reference Centre for Screening, Nijmegen, the Netherlands (MJMB)
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8
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van der Waal D, Ripping TM, Verbeek ALM, Broeders MJM. Breast cancer screening effect across breast density strata: A case-control study. Int J Cancer 2016; 140:41-49. [PMID: 27632020 DOI: 10.1002/ijc.30430] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2016] [Accepted: 08/30/2016] [Indexed: 12/24/2022]
Abstract
Breast cancer screening is known to reduce breast cancer mortality. A high breast density may affect this reduction. We assessed the effect of screening on breast cancer mortality in women with dense and fatty breasts separately. Analyses were performed within the Nijmegen (Dutch) screening programme (1975-2008), which invites women (aged 50-74 years) biennially. Performance measures were determined. Furthermore, a case-control study was performed for women having dense and women having fatty breasts. Breast density was assessed visually with a dichotomized Wolfe scale. Breast density data were available for cases. The prevalence of dense breasts among controls was estimated with age-specific rates from the general population. Sensitivity analyses were performed on these estimates. Screening performance was better in the fatty than in the dense group (sensitivity 75.7% vs 57.8%). The mortality reduction appeared to be smaller for women with dense breasts, with an odds ratio (OR) of 0.87 (95% CI 0.52-1.45) in the dense and 0.59 (95% CI 0.44-0.79) in the fatty group. We can conclude that high density results in lower screening performance and appears to be associated with a smaller mortality reduction. Breast density is thus a likely candidate for risk-stratified screening. More research is needed on the association between density and screening harms.
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Affiliation(s)
- Daniëlle van der Waal
- Radboud university medical center, Radboud Institute for Health Sciences, 6500 HB, Nijmegen, The Netherlands
| | - Theodora M Ripping
- Radboud university medical center, Radboud Institute for Health Sciences, 6500 HB, Nijmegen, The Netherlands
| | - André L M Verbeek
- Radboud university medical center, Radboud Institute for Health Sciences, 6500 HB, Nijmegen, The Netherlands
| | - Mireille J M Broeders
- Radboud university medical center, Radboud Institute for Health Sciences, 6500 HB, Nijmegen, The Netherlands.,Dutch Reference Centre for Screening, GJ 6503, Nijmegen, The Netherlands
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9
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Ripping TM, van der Waal D, Verbeek AL, Broeders MJ. The relative effect of mammographic screening on breast cancer mortality by socioeconomic status. Medicine (Baltimore) 2016; 95:e4335. [PMID: 27495038 PMCID: PMC4979792 DOI: 10.1097/md.0000000000004335] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
Breast cancer incidence and mortality are higher in women with a high socioeconomic status (SES). The potential to prevent death from breast cancer is therefore greater in the high SES group. This does, however, require that the effectiveness of screening in the high SES group is equal to or greater than the effectiveness in the low SES group. The aim of this study is to assess the relative effectiveness of mammographic screening on breast cancer mortality by SES.In Nijmegen, the Netherlands, women are invited to participate in biennial mammographic screening since 1975. Postal code is collected at each round and is used to calculate the SES of each woman based on the SES indicator of the Netherlands Institute for Social Research. The Dutch average was used to classify the SES score of each woman as either high or low. We designed a case-control study to investigate the effect of mammographic screening in women aged 50 to 75, 40 to 75, and 50 to 69 years, and calculated the odds ratios (ORs) and 95% confidence intervals (CIs).Among the women invited to the mammographic screening program in Nijmegen, 10% had a high SES. In women aged 50 to 75 years, the breast cancer death rate was 38% lower in screened women than in unscreened women. The ORs for women with high SES (OR 0.82, 95% CI 0.31-2.19) and low SES did not differ significantly (OR 0.61, 95% CI 0.47-0.78).Mammographic screening reduces breast cancer mortality, but we did not observe a significant difference in the relative effectiveness of screening by SES. If the effectiveness of mammographic screening is indeed not dependent on SES status, the absolute number of breast cancer deaths prevented by mammographic screening will be greater in the high SES than low SES group, because women with a high SES have a greater risk of breast cancer death.
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Affiliation(s)
- Theodora M. Ripping
- Radboud Institute for Health Sciences, Radboud University Medical Center
- Correspondence: Theodora M. Ripping, Radboud Institute of Health Sciences, Radboud University Medical Center, P.O. Box 9101 (Route 133), 6500 HB Nijmegen, the Netherlands (e-mail: )
| | | | - André L.M. Verbeek
- Radboud Institute for Health Sciences, Radboud University Medical Center
| | - Mireille J.M. Broeders
- Radboud Institute for Health Sciences, Radboud University Medical Center
- Dutch Reference Center for Screening, Nijmegen, the Netherlands
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10
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Heinävaara S, Sarkeala T, Anttila A. Impact of organised mammography screening on breast cancer mortality in a case-control and cohort study. Br J Cancer 2016; 114:1038-44. [PMID: 27010748 PMCID: PMC4984912 DOI: 10.1038/bjc.2016.68] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2015] [Revised: 02/19/2016] [Accepted: 02/25/2016] [Indexed: 11/09/2022] Open
Abstract
BACKGROUND The usefulness of case-control studies has been questioned. Our aim was to evaluate the long-term effect of screening on breast cancer mortality within the population-based mammography programme in Finland using a case-control design, and to compare the analyses with the earlier cohort study. METHODS The cases were women invited to screening, diagnosed and died from breast cancer in 1992-2011 while being 50-84 years at death. We chose 10 controls for each case with non-restrictive eligibility criteria. Our data included 1907 cases and 18 978 matched controls. We analysed associations between the screening participation and the risk of breast cancer death using the conditional Cox proportional hazards model. The effect estimates were corrected for self-selection bias. RESULTS An overall effect of screening was 0.67 (95% confidence interval (CI): 0.49-0.90), and that remained unchanged over time. Analyses with matching criteria comparable to the cohort study yielded an effect (0.70, 95% CI: 0.49-1.00) in 1992-2003 similar to that of the previous cohort analysis (0.72, 95% CI: 0.56-0.88). CONCLUSIONS Organised mammography screening decreases mortality from breast cancer by 33% among the participants. If made comparable, a case-cohort study can yield effect estimates similar to a cohort study.
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Affiliation(s)
- Sirpa Heinävaara
- Finnish Cancer Registry/Mass Screening Registry, Unioninkatu 22, 00130 Helsinki, Finland
| | - Tytti Sarkeala
- Finnish Cancer Registry/Mass Screening Registry, Unioninkatu 22, 00130 Helsinki, Finland
| | - Ahti Anttila
- Finnish Cancer Registry/Mass Screening Registry, Unioninkatu 22, 00130 Helsinki, Finland
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11
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Broeders M, Paci E. The Balance Sheet of Benefits and Harms of Breast Cancer Population-Based Screening in Europe: Outcome Research, Practice and Future Challenges. WOMENS HEALTH 2015; 11:883-90. [DOI: 10.2217/whe.15.34] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Breast cancer screening programs are still object of harsh debate. In 2012, the Independent UK Panel reviewed the benefits and harms of mammography screening based on randomized trials and the EUROSCREEN Working Group reviewed European observational outcome studies. The conclusion was that screening programs should continue, while acknowledging that harms, such as the occurrence of false-positive results and overdiagnosis, can have a negative impact on a woman's life. Information on the balance sheet of the benefits and harms of breast cancer screening should help women and their physicians to make an informed choice. The future challenge for breast screening programs is to assess the feasibility, acceptability, effectiveness and impact of risk-based screening in order to maximize benefit-to-harm ratios.
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Affiliation(s)
- Mireille Broeders
- Department for Health Evidence, Radboud University Medical Center, Nijmegen, The Netherlands
- Dutch Reference Centre for Screening, Nijmegen, The Netherlands
| | - Eugenio Paci
- Epidemiologist, Formerly at the Institute for Cancer Research and Prevention, Florence, Italy
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12
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Spix C, Berthold F, Hero B, Michaelis J, Schilling FH. Correction factors for self-selection when evaluating screening programmes. J Med Screen 2015. [DOI: 10.1177/0969141315597959] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Objective In screening programmes there is recognized bias introduced through participant self-selection (the healthy screenee bias). Methods used to evaluate screening programmes include Intention-to-screen, per-protocol, and the “post hoc” approach in which, after introducing screening for everyone, the only evaluation option is participants versus non-participants. All methods are prone to bias through self-selection. We present an overview of approaches to correct for this bias. Methods We considered four methods to quantify and correct for self-selection bias. Simple calculations revealed that these corrections are actually all identical, and can be converted into each other. Based on this, correction factors for further situations and measures were derived. The application of these correction factors requires a number of assumptions. Results Using as an example the German Neuroblastoma Screening Study, no relevant reduction in mortality or stage 4 incidence due to screening was observed. The largest bias (in favour of screening) was observed when comparing participants with non-participants. Conclusions Correcting for bias is particularly necessary when using the post hoc evaluation approach, however, in this situation not all required data are available. External data or further assumptions may be required for estimation.
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Affiliation(s)
- Claudia Spix
- University Medical Center Mainz, IMBEI, German Childhood Cancer Registry, Mainz, Germany
| | - Frank Berthold
- University Children’s Hospital, Pediatric Oncology/Hematology, Koeln, Germany
| | - Barbara Hero
- University Children’s Hospital, Pediatric Oncology/Hematology, Koeln, Germany
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13
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Tabár L, Yen AMF, Wu WYY, Chen SLS, Chiu SYH, Fann JCY, Ku MMS, Smith RA, Duffy SW, Chen THH. Insights from the Breast Cancer Screening Trials: How Screening Affects the Natural History of Breast Cancer and Implications for Evaluating Service Screening Programs. Breast J 2014; 21:13-20. [DOI: 10.1111/tbj.12354] [Citation(s) in RCA: 104] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Affiliation(s)
- László Tabár
- Department of Mammography; Central Hospital; Falun Sweden
| | | | - Wendy Yi-Ying Wu
- Graduate Institute of Epidemiology and Preventive Medicine; College of Public Health; National Taiwan University; Taipei Taiwan
| | | | - Sherry Yueh-Hsia Chiu
- Department and Graduate Institute of Health Care Management; Chang Gung University; Taoyuan Taiwan
| | - Jean Ching-Yuan Fann
- Department of Health Industry Management; College of Healthcare Management; Kainan University; Taoyuan Taiwan
| | - May Mei-Sheng Ku
- Graduate Institute of Epidemiology and Preventive Medicine; College of Public Health; National Taiwan University; Taipei Taiwan
| | | | - Stephen W Duffy
- Centre for Cancer Prevention; Wolfson Institute of Preventive Medicine; Queen Mary University of London; London UK
| | - Tony Hsiu-Hsi Chen
- Graduate Institute of Epidemiology and Preventive Medicine; College of Public Health; National Taiwan University; Taipei Taiwan
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14
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Coldman A, Phillips N, Wilson C, Decker K, Chiarelli AM, Brisson J, Zhang B, Payne J, Doyle G, Ahmad R. Pan-Canadian Study of Mammography Screening and Mortality from Breast Cancer. J Natl Cancer Inst 2014. [DOI: 10.1093/jnci/dju261 10.1093/jnci/dju404] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/05/2023] Open
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15
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Coldman A, Phillips N, Wilson C, Decker K, Chiarelli AM, Brisson J, Zhang B, Payne J, Doyle G, Ahmad R. Pan-Canadian Study of Mammography Screening and Mortality from Breast Cancer. ACTA ACUST UNITED AC 2014; 106:dju261. [DOI: 10.1093/jnci/dju261] [Citation(s) in RCA: 155] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
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16
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Paap E, Verbeek ALM, Botterweck AAM, van Doorne-Nagtegaal HJ, Imhof-Tas M, de Koning HJ, Otto SJ, de Munck L, van der Steen A, Holland R, den Heeten GJ, Broeders MJM. Breast cancer screening halves the risk of breast cancer death: a case-referent study. Breast 2014; 23:439-44. [PMID: 24713277 DOI: 10.1016/j.breast.2014.03.002] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2013] [Revised: 03/03/2014] [Accepted: 03/03/2014] [Indexed: 10/25/2022] Open
Abstract
Large-scale epidemiologic studies have consistently demonstrated the effectiveness of mammographic screening programs, however the benefits are still subject to debate. We estimated the effect of the Dutch screening program on breast cancer mortality. In a large multi-region case-referent study, we identified all breast cancer deaths in 2004 and 2005 in women aged 50-75 who had been invited for screening (cases). Cases were individually matched to referents from the population invited to screening. Conditional logistic regression was used to estimate the odds ratio (OR) of breast cancer death according to individual screening history. The OR was adjusted for self-selection bias using regional correction factors for the difference in baseline risk for breast cancer death between screened and unscreened women. A total of 1233 cases and 2090 referents were included in this study. We found a 58% reduction in breast cancer mortality in screened versus unscreened women (adjusted OR = 0.42, 95% CI 0.33-0.53). Screening, i.e. early detection and treatment, has resulted in a substantial reduction in breast cancer mortality, indicating that the Dutch breast cancer screening program is highly effective.
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Affiliation(s)
- Ellen Paap
- Department for Health Evidence, Radboud University Medical Center, Nijmegen, The Netherlands; National Expert and Training Centre for Breast Cancer Screening, Nijmegen, The Netherlands
| | - André L M Verbeek
- Department for Health Evidence, Radboud University Medical Center, Nijmegen, The Netherlands
| | | | | | - Mechli Imhof-Tas
- Department of Radiology, Radboud University Medical Center, Nijmegen, The Netherlands; Screening Program Early Detection of Breast Cancer in the Eastern Part of the Netherlands, Nijmegen, The Netherlands
| | - Harry J de Koning
- Department of Public Health, Erasmus MC, University Medical Center Rotterdam, Rotterdam, The Netherlands
| | - Suzie J Otto
- Department of Public Health, Erasmus MC, University Medical Center Rotterdam, Rotterdam, The Netherlands
| | - Linda de Munck
- Comprehensive Cancer Centre the Netherlands, Utrecht, The Netherlands
| | - Annemieke van der Steen
- Screening Program Early Detection of Breast Cancer in the South-West Part of the Netherlands, Vlaardingen, The Netherlands
| | - Roland Holland
- National Expert and Training Centre for Breast Cancer Screening, Nijmegen, The Netherlands
| | - Gerard J den Heeten
- National Expert and Training Centre for Breast Cancer Screening, Nijmegen, The Netherlands; Department of Radiology, Academic Medical Centre, University of Amsterdam, The Netherlands
| | - Mireille J M Broeders
- Department for Health Evidence, Radboud University Medical Center, Nijmegen, The Netherlands; National Expert and Training Centre for Breast Cancer Screening, Nijmegen, The Netherlands.
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17
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Hofvind S, Ursin G, Tretli S, Sebuødegård S, Møller B. Breast cancer mortality in participants of the Norwegian Breast Cancer Screening Program. Cancer 2013; 119:3106-12. [PMID: 23720226 PMCID: PMC4288930 DOI: 10.1002/cncr.28174] [Citation(s) in RCA: 85] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2013] [Revised: 04/12/2013] [Accepted: 04/17/2013] [Indexed: 12/02/2022]
Abstract
BACKGROUND The Norwegian Breast Cancer Screening Program started in 1996. To the authors' knowledge, this is the first report using individual-based data on invitation and participation to analyze breast cancer mortality among screened and nonscreened women in the program. METHODS Information on dates of invitation, attendance, breast cancer diagnosis, emigration, death, and cause of death was linked by using unique 11-digit personal identification numbers assigned all inhabitants of Norway at birth or immigration. In total, 699,628 women ages 50 to 69 years without prior a diagnosis of breast cancer were invited to the program from 1996 to 2009 and were followed for breast cancer through 2009 and death through 2010. Incidence-based breast cancer mortality rate ratios (MRRs) were compared between the screened and nonscreened cohorts using a Poisson regression model. The MRRs were adjusted for calendar period, attained age, years since inclusion in the cohorts, and self-selection bias. RESULTS The crude breast cancer mortality rate was 20.7 per 100,000 women-years for the screened cohort compared with 39.7 per 100,000 women-years for the nonscreened cohort, resulting in an MRR of 0.52 (95% confidence interval, 0.47-0.59). The mortality reduction associated with attendance in the program was 43% (MRR, 0.57; 95% confidence interval, 0.51-0.64) after adjusting for calendar period, attained age, years after inclusion in the cohort, and self-selection bias. CONCLUSIONS After 15 years of follow-up, a 43% reduction in mortality was observed among women who attended the national mammographic screening program in Norway.
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Affiliation(s)
- Solveig Hofvind
- Department of Research, Cancer Registry of NorwayOslo, Norway
- Oslo and Akershus University College of Applied SciencesOslo, Norway
| | - Giske Ursin
- Cancer Registry of NorwayOslo, Norway
- Institute of Basic Medical Sciences, University of OsloOslo, Norway
- Department of Preventive Medicine, University of Southern CaliforniaLos Angeles, California
| | - Steinar Tretli
- Department of Research, Cancer Registry of NorwayOslo, Norway
- The Norwegian University of Science and TechnologyTrondhjem, Norway
| | | | - Bjørn Møller
- Department of Registration, Cancer Registry of NorwayOslo, Norway
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18
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Broeders M, Moss S, Nyström L, Njor S, Jonsson H, Paap E, Massat N, Duffy S, Lynge E, Paci E. The impact of mammographic screening on breast cancer mortality in Europe: a review of observational studies. J Med Screen 2013; 19 Suppl 1:14-25. [PMID: 22972807 DOI: 10.1258/jms.2012.012078] [Citation(s) in RCA: 270] [Impact Index Per Article: 24.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
OBJECTIVES To assess the impact of population-based mammographic screening on breast cancer mortality in Europe, considering different methodologies and limitations of the data. METHODS We conducted a systematic literature review of European trend studies (n = 17), incidence-based mortality (IBM) studies (n = 20) and case-control (CC) studies (n = 8). Estimates of the reduction in breast cancer mortality for women invited versus not invited and/or for women screened versus not screened were obtained. The results of IBM studies and CC studies were each pooled using a random effects meta-analysis. RESULTS Twelve of the 17 trend studies quantified the impact of population-based screening on breast cancer mortality. The estimated breast cancer mortality reductions ranged from 1% to 9% per year in studies reporting an annual percentage change, and from 28% to 36% in those comparing post- and prescreening periods. In the IBM studies, the pooled mortality reduction was 25% (relative risk [RR] 0.75, 95% confidence interval [CI] 0.69-0.81) among invited women and 38% (RR 0.62, 95% CI 0.56-0.69) among those actually screened. The corresponding pooled estimates from the CC studies were 31% (odds ratio [OR] 0.69, 95% CI 0.57-0.83), and 48% (OR 0.52, 95% CI 0.42-0.65) adjusted for self-selection. CONCLUSIONS Valid observational designs are those where sufficient longitudinal individual data are available, directly linking a woman's screening history to her cause of death. From such studies, the best 'European' estimate of breast cancer mortality reduction is 25-31% for women invited for screening, and 38-48% for women actually screened. Much of the current controversy on breast cancer screening is due to the use of inappropriate methodological approaches that are unable to capture the true effect of mammographic screening.
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Affiliation(s)
- Mireille Broeders
- Department of Epidemiology, Biostatistics and HTA, Radboud University Nijmegen Medical Centre & National Expert and Training Centre for Breast Cancer Screening, Nijmegen, The Netherlands.
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19
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Otto SJ, Fracheboud J, Verbeek AL, Boer R, Reijerink-Verheij JC, Otten JD, Broeders MJ, de Koning HJ. Mammography Screening and Breast Cancer Mortality—Response. Cancer Epidemiol Biomarkers Prev 2012. [DOI: 10.1158/1055-9965.epi-12-0235] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
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