Karsten Juhl Jørgensen, MD, DrMedSci; Peter C. Gøtzsche, MD, MSc; Mette Kalager, MD, PhD (*); Per-Henrik Zahl, MD, DrMedSci (*)
Disclosures: Authors have disclosed no conflicts of interest. Forms can be viewed at www.acponline.org/authors/icmje/ConflictOfInterestForms.do?msNum=M16-0270.
Editors' Disclosures: Christine Laine, MD, MPH, Editor in Chief, reports that she has no financial relationships or interests to disclose. Darren B. Taichman, MD, PhD, Executive Deputy Editor, reports that he has no financial relationships or interests to disclose. Cynthia D. Mulrow, MD, MSc, Senior Deputy Editor, reports that she has no relationships or interests to disclose. Deborah Cotton, MD, MPH, Deputy Editor, reports that she has no financial relationships or interest to disclose. Jaya K. Rao, MD, MHS, Deputy Editor, reports that she has stock holdings/options in Eli Lilly and Pfizer. Sankey V. Williams, MD, Deputy Editor, reports that he has no financial relationships or interests to disclose. Catharine B. Stack, PhD, MS, Deputy Editor for Statistics, reports that she has stock holdings in Pfizer and Johnson & Johnson.
Reproducible Research Statement:Study protocol and statistical code: Available from Dr. Jørgensen (e-mail, firstname.lastname@example.org). Data set: The aggregated statistical data available from Dr. Jørgensen (e-mail, email@example.com); however, under Danish legislation, the authors are not at liberty to share individual-patient data from registries.
Requests for Single Reprints: Karsten Juhl Jørgensen, MD, DrMedSci, The Nordic Cochrane Centre, Rigshospitalet, Department 7811, Blegdamsvej 9, DK-2100 Copenhagen, Denmark; e-mail, firstname.lastname@example.org.
Current Author Addresses: Drs. Jørgensen and Gøtzsche: The Nordic Cochrane Centre, Rigshospitalet, Department 7811, Blegdamsvej 9, DK-2100 Copenhagen, Denmark.
Dr. Kalager: University of Oslo, Institute of Health and Society, Department of Health Management and Health Economics, PO Box 1089, Blindern, 0318 Oslo, Norway.
Dr. Zahl: Norwegian Institute of Public Health, PO Box 4404, Nydalen, N-0403 Oslo, Norway.
Author Contributions: Conception and design: K.J. Jørgensen, P.C. Gøtzsche, M. Kalager, P.H. Zahl.
Analysis and interpretation of the data: K.J. Jørgensen, P.C. Gøtzsche, M. Kalager, P.H. Zahl.
Drafting of the article: K.J. Jørgensen, M. Kalager, P.H. Zahl.
Critical revision of the article for important intellectual content: K.J. Jørgensen, P.C. Gøtzsche, M. Kalager, P.H. Zahl.
Final approval of the article: K.J. Jørgensen, P.C. Gøtzsche, M. Kalager, P.H. Zahl.
Statistical expertise: K.J. Jørgensen, M. Kalager, P.H. Zahl.
Administrative, technical, or logistic support: P.C. Gøtzsche.
Collection and assembly of data: P.H. Zahl.
Jørgensen KJ, Gøtzsche PC, Kalager M, Zahl P. Breast Cancer Screening in Denmark: A Cohort Study of Tumor Size and Overdiagnosis. Ann Intern Med. [Epub ahead of print 10 January 2017]:. doi: 10.7326/M16-0270
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Published: Ann Intern Med. 2017.
Effective breast cancer screening should detect early-stage cancer and prevent advanced disease.
To assess the association between screening and the size of detected tumors and to estimate overdiagnosis (detection of tumors that would not become clinically relevant).
Denmark from 1980 to 2010.
Women aged 35 to 84 years.
Screening programs offering biennial mammography for women aged 50 to 69 years beginning in different regions at different times.
Trends in the incidence of advanced (>20 mm) and nonadvanced (≤20 mm) breast cancer tumors in screened and nonscreened women were measured. Two approaches were used to estimate the amount of overdiagnosis: comparing the incidence of advance and nonadvanced tumors among women aged 50 to 84 years in screening and nonscreening areas; and comparing the incidence for nonadvanced tumors among women aged 35 to 49, 50 to 69, and 70 to 84 years in screening and nonscreening areas.
Screening was not associated with lower incidence of advanced tumors. The incidence of nonadvanced tumors increased in the screening versus prescreening periods (incidence rate ratio, 1.49 [95% CI, 1.43 to 1.54]). The first estimation approach found that 271 invasive breast cancer tumors and 179 ductal carcinoma in situ (DCIS) lesions were overdiagnosed in 2010 (overdiagnosis rate of 24.4% [including DCIS] and 14.7% [excluding DCIS]). The second approach, which accounted for regional differences in women younger than the screening age, found that 711 invasive tumors and 180 cases of DCIS were overdiagnosed in 2010 (overdiagnosis rate of 48.3% [including DCIS] and 38.6% [excluding DCIS]).
Regional differences complicate interpretation.
Breast cancer screening was not associated with a reduction in the incidence of advanced cancer. It is likely that 1 in every 3 invasive tumors and cases of DCIS diagnosed in women offered screening represent overdiagnosis (incidence increase of 48.3%).
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Breast Cancer, Cancer Screening/Prevention, Hematology/Oncology, Prevention/Screening.
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