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. 2006;8(6):R68.
doi: 10.1186/bcr1625.

Estimate of overdiagnosis of breast cancer due to mammography after adjustment for lead time. A service screening study in Italy

Eugenio Paci  1 , Guido Miccinesi, Donella Puliti, Paola Baldazzi, Vincenzo De Lisi, Fabio Falcini, Claudia Cirilli, Stefano Ferretti, Lucia Mangone, Alba Carola Finarelli, Stefano Rosso, Nereo Segnan, Fabrizio Stracci, Adele Traina, Rosario Tumino, Manuel Zorzi
Affiliations

Estimate of overdiagnosis of breast cancer due to mammography after adjustment for lead time. A service screening study in Italy

Eugenio Paci et al. Breast Cancer Res. 2006.

Abstract

Introduction: Excess of incidence rates is the expected consequence of service screening. The aim of this paper is to estimate the quota attributable to overdiagnosis in the breast cancer screening programmes in Northern and Central Italy.

Methods: All patients with breast cancer diagnosed between 50 and 74 years who were resident in screening areas in the six years before and five years after the start of the screening programme were included. We calculated a corrected-for-lead-time number of observed cases for each calendar year. The number of observed incident cases was reduced by the number of screen-detected cases in that year and incremented by the estimated number of screen-detected cases that would have arisen clinically in that year.

Results: In total we included 13,519 and 13,999 breast cancer cases diagnosed in the pre-screening and screening years, respectively. In total, the excess ratio of observed to predicted in situ and invasive cases was 36.2%. After correction for lead time the excess ratio was 4.6% (95% confidence interval 2 to 7%) and for invasive cases only it was 3.2% (95% confidence interval 1 to 6%).

Conclusion: The remaining excess of cancers after individual correction for lead time was lower than 5%.

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Figures

Figure 1
Figure 1
Natural history of breast cancer and screening.
Figure 2
Figure 2
Incremental and decremental cases in a cohort of women aged 64 years at entry.
Figure 3
Figure 3
Breast cancer incidence rates by method of detection, on the screening time scale. The participants were aged 50 to 74 years. SD, screen detected; NSD, not screen detected.
Figure 4
Figure 4
Breast cancer incidence rates predicted, observed, and observed corrected for lead time. The participants were aged 50 to 74 years.
Figure 5
Figure 5
Breast cancer incidence rates by age group and years since the start of the screening.
Figure 6
Figure 6
Breast cancer incidence rates predicted, observed, and observed corrected for lead time. The age groups at first invitation were as follows: (a) 50 to 54 years; (b) 55 to 59 years; (c) 60 to 64 years; (d) 65 to 69 years; (e) 70 to 74 years.
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References

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