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Absolute numbers of lives saved and overdiagnosis in breast cancer screening, from a randomized trial and from the Breast Screening Programme in England.

Duffy SW, Tabar L, Olsen AH, Vitak B, Allgood PC, Chen TH, Yen AM, Smith RA - J Med Screen (2010)

Bottom Line: We used Poisson regression for statistical inference.The benefit of mammographic screening in terms of lives saved is greater in absolute terms than the harm in terms of overdiagnosis.Between 2 and 2.5 lives are saved for every overdiagnosed case.

View Article: PubMed Central - PubMed

Affiliation: CR-UK Centre for Epidemiology, Statistics and Mathematics, Wolfson Institute for Preventive Medicine, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, Charterhouse Square, London EC1M 6BQ, UK.

ABSTRACT

Objectives: To estimate the absolute numbers of breast cancer deaths prevented and the absolute numbers of tumours overdiagnosed in mammographic screening for breast cancer at ages 50-69 years.

Setting: The Swedish Two-County randomized trial of mammographic screening for breast cancer, and the UK Breast Screening Programme in England, ages 50-69 years.

Methods: We estimated the absolute numbers of deaths avoided and additional cases diagnosed in the study group (active study population) of the Swedish Two-County Trial, by comparison with the control group (passive study population). We estimated the same quantities for the mortality and incidence rates in England (1974-2004 and 1974-2003, respectively). We used Poisson regression for statistical inference.

Results: A substantial and significant reduction in breast cancer mortality was associated with screening in both the Two-County Trial (P < 0.001) and the screening programme in England (P < 0.001). The absolute benefits were estimated as 8.8 and 5.7 breast cancer deaths prevented per 1000 women screened for 20 years starting at age 50 from the Two-County Trial and screening programme in England, respectively. The corresponding estimated numbers of cases overdiagnosed per 1000 women screened for 20 years were, respectively, 4.3 and 2.3 per 1000.

Conclusions: The benefit of mammographic screening in terms of lives saved is greater in absolute terms than the harm in terms of overdiagnosis. Between 2 and 2.5 lives are saved for every overdiagnosed case.

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Related in: MedlinePlus

Breast cancer mortality in England 1974–2004
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JMS-09094F1: Breast cancer mortality in England 1974–2004

Mentions: Figure 1 shows breast cancer mortality in England by time for age groups <50, 50–69 and 70+. There was a sharp decrease in mortality from the mid-1990s in the age group 50–69. In women aged <50, there was a lesser reduction in mortality, although this is difficult to see in the figure due to the rarity of breast cancer at younger ages. In the 70+ age group, there was a rise in mortality in the early 1990s then a fall back to 1980s' levels. Table 2 shows the mortality rates and RRs for the three age groups, and periods 1974–1988, 1989–1994 and 1995 onwards. The table also shows observed and expected numbers of deaths in 1995 onwards. Compared with other age groups there was a highly significant 28% reduction in breast cancer mortality in the age group invited to screening (RR 0.72, 95% CI 0.70–0.74, P < 0.001). The deficit in breast cancer deaths was 53,057–38,201 = 14,856. This corresponds to approximately 52 million person-years of screening, which implies 5.7 breast cancer deaths prevented for 1000 women screened for 20 years.


Absolute numbers of lives saved and overdiagnosis in breast cancer screening, from a randomized trial and from the Breast Screening Programme in England.

Duffy SW, Tabar L, Olsen AH, Vitak B, Allgood PC, Chen TH, Yen AM, Smith RA - J Med Screen (2010)

Breast cancer mortality in England 1974–2004
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3104821&req=5

JMS-09094F1: Breast cancer mortality in England 1974–2004
Mentions: Figure 1 shows breast cancer mortality in England by time for age groups <50, 50–69 and 70+. There was a sharp decrease in mortality from the mid-1990s in the age group 50–69. In women aged <50, there was a lesser reduction in mortality, although this is difficult to see in the figure due to the rarity of breast cancer at younger ages. In the 70+ age group, there was a rise in mortality in the early 1990s then a fall back to 1980s' levels. Table 2 shows the mortality rates and RRs for the three age groups, and periods 1974–1988, 1989–1994 and 1995 onwards. The table also shows observed and expected numbers of deaths in 1995 onwards. Compared with other age groups there was a highly significant 28% reduction in breast cancer mortality in the age group invited to screening (RR 0.72, 95% CI 0.70–0.74, P < 0.001). The deficit in breast cancer deaths was 53,057–38,201 = 14,856. This corresponds to approximately 52 million person-years of screening, which implies 5.7 breast cancer deaths prevented for 1000 women screened for 20 years.

Bottom Line: We used Poisson regression for statistical inference.The benefit of mammographic screening in terms of lives saved is greater in absolute terms than the harm in terms of overdiagnosis.Between 2 and 2.5 lives are saved for every overdiagnosed case.

View Article: PubMed Central - PubMed

Affiliation: CR-UK Centre for Epidemiology, Statistics and Mathematics, Wolfson Institute for Preventive Medicine, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, Charterhouse Square, London EC1M 6BQ, UK.

ABSTRACT

Objectives: To estimate the absolute numbers of breast cancer deaths prevented and the absolute numbers of tumours overdiagnosed in mammographic screening for breast cancer at ages 50-69 years.

Setting: The Swedish Two-County randomized trial of mammographic screening for breast cancer, and the UK Breast Screening Programme in England, ages 50-69 years.

Methods: We estimated the absolute numbers of deaths avoided and additional cases diagnosed in the study group (active study population) of the Swedish Two-County Trial, by comparison with the control group (passive study population). We estimated the same quantities for the mortality and incidence rates in England (1974-2004 and 1974-2003, respectively). We used Poisson regression for statistical inference.

Results: A substantial and significant reduction in breast cancer mortality was associated with screening in both the Two-County Trial (P < 0.001) and the screening programme in England (P < 0.001). The absolute benefits were estimated as 8.8 and 5.7 breast cancer deaths prevented per 1000 women screened for 20 years starting at age 50 from the Two-County Trial and screening programme in England, respectively. The corresponding estimated numbers of cases overdiagnosed per 1000 women screened for 20 years were, respectively, 4.3 and 2.3 per 1000.

Conclusions: The benefit of mammographic screening in terms of lives saved is greater in absolute terms than the harm in terms of overdiagnosis. Between 2 and 2.5 lives are saved for every overdiagnosed case.

Show MeSH
Related in: MedlinePlus