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 Posted: Wed Nov 19, 2008 4:58 pm Post subject: Estimate of Overdiagnosis of Breast Cancer due to Mammograph |
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http://www.medscape.com/viewarticle/551700
From Breast Cancer Research
Estimate of Overdiagnosis of Breast Cancer due to Mammography After
Adjustment for Lead Time. A Service Screening Study in Italy
Posted 02/21/2007
Eugenio Paci; 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
Author Information
Abstract and Introduction
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%.
Introduction
Breast cancer service screening programmes have been implemented on a
regional basis in several Italian areas. Most screening programmes are
participants in the national survey promoted by the Italian Group for
Mammography Screening[1] and have collected performance data in accordance
with the European guidelines for breast cancer screening.[2,3]
Early diagnosis of breast cancer and excess incidence are the expected
consequences of breast cancer screening. The possible detection at
screening of breast cancers that would not have been diagnosed in the
absence of screening over a subject>s lifetime has been defined as
overdiagnosis.[4,5]
In this paper we present observational data from a large Italian study -
the Impact Study - in which we apply a statistical model for monitoring
service screening to forecast the possible occurrence of overdiagnosis.
This study is based on the evaluation of individual cases and not on
aggregated data, which have been used in most studies evaluating service
screening so far. |
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