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Showing content from https://pubmed.ncbi.nlm.nih.gov/27732805/ below:

Breast-Cancer Tumor Size, Overdiagnosis, and Mammography Screening Effectiveness

. 2016 Oct 13;375(15):1438-1447. doi: 10.1056/NEJMoa1600249. Breast-Cancer Tumor Size, Overdiagnosis, and Mammography Screening Effectiveness

Affiliations

Affiliation

¹ From the Dartmouth Institute for Health Policy and Clinical Practice, Lebanon (H.G.W., A.J.O.), and the Departments of Medicine (H.G.W.) and Biomedical Data Science (A.J.O.), Geisel School of Medicine, Hanover - both in New Hampshire; and the Division of Cancer Prevention, National Cancer Institute, Bethesda, MD (P.C.P., B.S.K.).

PMID: 27732805
DOI: 10.1056/NEJMoa1600249

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Breast-Cancer Tumor Size, Overdiagnosis, and Mammography Screening Effectiveness

H Gilbert Welch et al. N Engl J Med. 2016.

Free article . 2016 Oct 13;375(15):1438-1447. doi: 10.1056/NEJMoa1600249. Affiliation

¹ From the Dartmouth Institute for Health Policy and Clinical Practice, Lebanon (H.G.W., A.J.O.), and the Departments of Medicine (H.G.W.) and Biomedical Data Science (A.J.O.), Geisel School of Medicine, Hanover - both in New Hampshire; and the Division of Cancer Prevention, National Cancer Institute, Bethesda, MD (P.C.P., B.S.K.).

PMID: 27732805
DOI: 10.1056/NEJMoa1600249

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Abstract

Background: The goal of screening mammography is to detect small malignant tumors before they grow large enough to cause symptoms. Effective screening should therefore lead to the detection of a greater number of small tumors, followed by fewer large tumors over time.

Methods: We used data from the Surveillance, Epidemiology, and End Results (SEER) program, 1975 through 2012, to calculate the tumor-size distribution and size-specific incidence of breast cancer among women 40 years of age or older. We then calculated the size-specific cancer case fatality rate for two time periods: a baseline period before the implementation of widespread screening mammography (1975 through 1979) and a period encompassing the most recent years for which 10 years of follow-up data were available (2000 through 2002).

Results: After the advent of screening mammography, the proportion of detected breast tumors that were small (invasive tumors measuring <2 cm or in situ carcinomas) increased from 36% to 68%; the proportion of detected tumors that were large (invasive tumors measuring ≥2 cm) decreased from 64% to 32%. However, this trend was less the result of a substantial decrease in the incidence of large tumors (with 30 fewer cases of cancer observed per 100,000 women in the period after the advent of screening than in the period before screening) and more the result of a substantial increase in the detection of small tumors (with 162 more cases of cancer observed per 100,000 women). Assuming that the underlying disease burden was stable, only 30 of the 162 additional small tumors per 100,000 women that were diagnosed were expected to progress to become large, which implied that the remaining 132 cases of cancer per 100,000 women were overdiagnosed (i.e., cases of cancer were detected on screening that never would have led to clinical symptoms). The potential of screening to lower breast cancer mortality is reflected in the declining incidence of larger tumors. However, with respect to only these large tumors, the decline in the size-specific case fatality rate suggests that improved treatment was responsible for at least two thirds of the reduction in breast cancer mortality.

Conclusions: Although the rate of detection of large tumors fell after the introduction of screening mammography, the more favorable size distribution was primarily the result of the additional detection of small tumors. Women were more likely to have breast cancer that was overdiagnosed than to have earlier detection of a tumor that was destined to become large. The reduction in breast cancer mortality after the implementation of screening mammography was predominantly the result of improved systemic therapy.

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Comment in

Breast-Cancer Tumor Size and Screening Effectiveness.
Welch HG, Prorok PC, Kramer BS. Welch HG, et al. N Engl J Med. 2017 Jan 5;376(1):94-5. doi: 10.1056/NEJMc1614282. N Engl J Med. 2017. PMID: 28052230 No abstract available.
Breast-Cancer Tumor Size and Screening Effectiveness.
Brentnall AR, Duffy SW, Cuzick J. Brentnall AR, et al. N Engl J Med. 2017 Jan 5;376(1):94. doi: 10.1056/NEJMc1614282. N Engl J Med. 2017. PMID: 28052231 No abstract available.
Breast-Cancer Tumor Size and Screening Effectiveness.
Jatoi I, Anderson WF. Jatoi I, et al. N Engl J Med. 2017 Jan 5;376(1):93. doi: 10.1056/NEJMc1614282. N Engl J Med. 2017. PMID: 28060474 No abstract available.
Breast-Cancer Tumor Size and Screening Effectiveness.
Kopans DB. Kopans DB. N Engl J Med. 2017 Jan 5;376(1):93-4. doi: 10.1056/NEJMc1614282. N Engl J Med. 2017. PMID: 28060475 No abstract available.
More misinformation on breast cancer screening.
Kopans DB. Kopans DB. Gland Surg. 2017 Feb;6(1):125-129. doi: 10.21037/gs.2016.12.15. Gland Surg. 2017. PMID: 28210564 Free PMC article.
Both a stage shift and changes in stage-specific survival have contributed to reductions in breast cancer mortality.
Duffy SW, Etzioni R, Sasieni P. Duffy SW, et al. Evid Based Med. 2017 Apr;22(2):76. doi: 10.1136/ebmed-2016-110632. Epub 2017 Feb 22. Evid Based Med. 2017. PMID: 28228386 No abstract available.
Impact of assumptions - the example of the Welch-analysis of mammography screening effectiveness.
Lynge E, Beau AB, Lophaven S. Lynge E, et al. Acta Oncol. 2017 Aug;56(8):1131-1133. doi: 10.1080/0284186X.2017.1288921. Epub 2017 Feb 17. Acta Oncol. 2017. PMID: 28488450 No abstract available.