Authors' objectives: The Alberta Clinical Practice Guidelines Program, as part of its process for updating the clinical practice guidelines (CPG) on breast cancer screening, requested a review of the current evidence. The three objectives of this assessment are to determine the available scientific evidence on: 1. The effective time interval for mammography screening in asymptomatic women aged 50 to 69 years 2. The effective screening interval in asymptomatic women between the ages of 40 and 49 years 3. The mortality rate reduction of mammography screening in asymptomatic women aged 40 to 49 years.

Authors' results and conclusions: The evidence from the eight RCTs does not provide clear answers to the questions of when to start screening, when to stop screening or how often to screen. These trials focused on the determination of the efficacy of mammography screening alone or in combination with CBE in women aged 40 to 74 years of age. Despite all of the differences in the RCTs (including screening intervals) conducted to date, these trials have consistently demonstrated a reduction in breast cancer mortality among screened women aged 40 to 74 years with screening intervals from 12 to 33 months. Even though combining and re-analyzing data in a meta analysis involves assumptions, and disagreement persists as to the level of statistical significance of the mortality reduction resulting from mammography screening for women aged 40 to 49 years, there is general agreement on two findings. First, mortality reduction is smaller for younger women compared to older women and, second, the interval between the initiation of mammography screening and the appearance of any mortality benefit is considerably longer for younger women. A current multicentre RCT in the U.K. attempts to address the efficacy of commencing annual mammography screening in asymptomatic women at the age of 40 and 41 years over a 10 year time period. It will not provide an answer about the appropriate screening intervals for this age group. Nor has any trial been designed to determine the appropriate screening interval for asymptomatic women over the age of 50 years.

Authors' recommendations: - Results from RCTs and meta analyses have demonstrated a significant reduction in breast cancer mortality among screened women aged 50 years and over with screening intervals ranging from 12 months to 33 months. - Effectiveness of screening asymptomatic women aged 40 to 49 years remains unresolved. - Uncontrolled, retrospective studies, considered to be low level of evidence, were available to determine the appropriate screening intervals for different age groups. These studies provided inconclusive evidence. - Efficacy of annual mammography screening in asymptomatic women commencing at ages 40 and 41 years will be addressed by a UK RCT.

Authors' methods: Systematic review

Project Status: Completed

Year Published: 2000

URL for published report: http://www.ihe.ca/advanced-search/mammography-screening-mortality-rate-reduction-and-screening-interval

English language abstract: An English language summary is available

Publication Type: Not Assigned

Country: Canada

Organisation Name: Institute of Health Economics

Contact Address: 1200, 10405 Jasper Avenue, Edmonton, Alberta, Canada, T5J 3N4. Tel: +1 780 448 4881; Fax: +1 780 448 0018;

Contact Name: djuzwishin@ihe.ca

Contact Email: djuzwishin@ihe.ca

Copyright: <p>Alberta Heritage Foundation for Medical Research (AHFMR)</p>