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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 incidence in England 1974–2003
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JMS-09094F2: Breast cancer incidence in England 1974–2003

Mentions: Figure 2 shows breast cancer incidence in England by age and time. Clearly, incidence was increasing prior to screening in all age groups and continued to do so thereafter, with a particular strong increase in age group 50–64 in the early years of the programme. A corresponding deficit can be seen shortly afterwards in the 65–69 age group, which also showed a sharp increase in 2002–2003 when the programme was expanded to include ages up to 70 years. At ages 70 years or more the incidence after 1996 was lower than that which would have been observed if prescreening trends had persisted. Table 3 shows the observed and expected numbers of cases by age group in years 1989–2003, standardized to the age group <45. There was an excess of a total of 25,042 tumours in age groups 45–64, but a deficit of 18,981 in ages 65 years and over. The net excess was therefore 6061 breast cancers. Taking this as the estimate of overdiagnosis from the 52 million person-years of screening, we estimate 2.3 cases overdiagnosed per 1000 women screened for 20 years. Thus, for every two breast cancer deaths prevented in the UK programme, we estimate that there is less than one overdiagnosed case. And for approximately every 28 cases diagnosed, 2.5 lives were saved and one case overdiagnosed. The larger number of tumours diagnosed per life saved and per overdiagnosed case is due to the higher incidence and greater survival in the late 1990s and early 21st century compared with the late 1970s and early 1980s.


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 incidence in England 1974–2003
© Copyright Policy - open-access
Related In: Results  -  Collection

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

JMS-09094F2: Breast cancer incidence in England 1974–2003
Mentions: Figure 2 shows breast cancer incidence in England by age and time. Clearly, incidence was increasing prior to screening in all age groups and continued to do so thereafter, with a particular strong increase in age group 50–64 in the early years of the programme. A corresponding deficit can be seen shortly afterwards in the 65–69 age group, which also showed a sharp increase in 2002–2003 when the programme was expanded to include ages up to 70 years. At ages 70 years or more the incidence after 1996 was lower than that which would have been observed if prescreening trends had persisted. Table 3 shows the observed and expected numbers of cases by age group in years 1989–2003, standardized to the age group <45. There was an excess of a total of 25,042 tumours in age groups 45–64, but a deficit of 18,981 in ages 65 years and over. The net excess was therefore 6061 breast cancers. Taking this as the estimate of overdiagnosis from the 52 million person-years of screening, we estimate 2.3 cases overdiagnosed per 1000 women screened for 20 years. Thus, for every two breast cancer deaths prevented in the UK programme, we estimate that there is less than one overdiagnosed case. And for approximately every 28 cases diagnosed, 2.5 lives were saved and one case overdiagnosed. The larger number of tumours diagnosed per life saved and per overdiagnosed case is due to the higher incidence and greater survival in the late 1990s and early 21st century compared with the late 1970s and early 1980s.

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