Modelling the overdiagnosis of breast cancer due to mammography screening in women aged 40-49 in the United Kingdom
A partir de données issues d'un essai randomisé de dépistage du cancer du sein par mammographie annuelle à partir de 40 ans chez des femmes britanniques, cette étude évalue le taux de surdiagnostic dans la population des femmes d'âge compris entre 40 et 49 ans
INTRODUCTION:Overdiagnosis of breast cancer due to mammography screening, defined as the diagnosis of screen-detected cancers which would not have presented clinically in a women's lifetime in the absence of screening, has emerged as a highly contentious issue, as harm caused may question the benefit of mammographic screening. Most studies included women over 50 years old and little information is available for younger women.
METHODS:We estimated the overdiagnosis of breast cancer due to screening in women aged 40-49 years using data from a randomized trial of annual mammographic screening starting age 40 conducted in the UK. A six-state Markov model was constructed to estimate the sensitivity of mammography for invasive and in-situ breast cancer and the screen-detectable mean sojourn time for non-progressive in-situ, progressive in-situ, and invasive breast cancer. Then, a 10-state simulation model of cancer progression, screening, and death, was developed to estimate overdiagnosis attributable to screening.
RESULTS:The sensitivity of mammography for invasive and in-situ breast cancers was 90% (95% CI 72-99) and 82% (43-99), respectively. The screen-detectable mean sojourn time of preclinical non-progressive and progressive in-situ cancers was 1.3 (0.4-3.4) and 0.11 (0.05-0.19) years, respectively, and 0.8 years (0.6-1.2) for preclinical invasive breast cancer. The proportion of screen-detected in-situ cancers that were non-progressive was 55% (25-77) for the first and 40% (22-60) for subsequent screens. In our main analysis, overdiagnosis was estimated as 0.7% of screen-detected cancers. A sensitivity analysis, covering a wide range of alternative scenarios, yielded a range of 0.5% to 2.9%.
CONCLUSION:Although a high proportion of screen-detected in-situ cancers were non-progressive, a majority of these would have presented clinically in the absence of screening. The extent of overdiagnosis due to screening in women aged 40-49 was small. Results also suggest annual screening is most suitable for women aged 40-49 in the United Kingdom due to short cancer sojourn times.
Breast Cancer Research , article en libre accès, 2011