Revised estimates of overdiagnosis from the Canadian National Breast Screening Study
A partir de données portant sur 89 835 femmes incluses dans un essai sur le dépistage du cancer du sein par mammographie au Canada (50 430 femmes d'âge compris entre 40 et 49 ans, 39 405 femmes d'âge compris entre 50 et 59 ans), cette étude estime le taux de surdiagnostic associé au dépistage en fonction de l'âge des participantes (durée de suivi : 25 ans)
We have re-estimated overdiagnosis of breast cancer from mammography screening by age group in the Canadian National Breast Screening Study (CNBSS), a randomized screening trial. In the CNBSS, participants were recruited in 15 centers. 89,835 women were randomized with informed consent, 50,430 age 40–49 and 39,405 age 50–59. Women aged 40–49 received annual mammography and physical examination (MA + PX) versus a single physical examination and usual care in the community (UC). Women aged 50–59 received (MA + PX) versus (PX-alone) annually. Individual randomization resulted in 44 almost identically distributed demographic and risk factors. Annual compliance over the five or four scheduled screens was 86–95%. The cumulative numbers of invasive and in situ breast cancers ascertained by year during screening and subsequent follow-up to 25 years post entry to the CNBSS in the mammography arm have been compared to those in the control arm. Estimates of overdiagnosis were derived using post-screening cessation cut-off points from 1 to 20 years.⋯ Overdiagnosis of invasive breast cancer at five years post cessation of screening for women aged 40–49 was estimated to be 32%, and 16% for women aged 50–59; 20 years post cessation of screening 48% for women 40–49 and 5% for those 50–59. Including ductal carcinoma in situ with invasive cancer, estimates were 41%, 25%, 55% and 16%, respectively. We conclude that approximately 30% of invasive screen-detected breast cancers in women age 40–49 were overdiagnosed, and 20% of those screen-detected in women age 50–59. Including ductal carcinoma in situ, the estimates are 40% and 30%, respectively.
Preventive Medicine , résumé, 2015