The review of randomization in the Canadian National Breast Screening Study: What does the verdict mean for clinicians?

Abstract

What is the practising clinician to make of the review by Drs. John C. Bailar III and Brian MacMahon (see pages 193 to 199 of this issue) of the randomization procedure used in the Canadian National Breast Screening Study? Their conclusion that any flaws in randomization would not have affected the published data is reassuring. Nevertheless, the review has not resolved the controversy surrounding the recommendations for screening mammography for women aged 40-49. Recommendations must be based on strong evidence that the benefits of population-based testing outweigh the harms. The absence of such evidence for women aged 40-49 should not, however, preclude the use of mammography as a diagnostic test for women in their 40s whose clinical signs require follow-up. Mammography could also be considered for women whose family history or other factors suggest an increased risk for breast cancer, provided that the limitations and potential disadvantages of testing are explained.