What Canadians Should Know About the Canadian National Breast Screening Studies

Update Oct. 8, 2021: To view this and all other webinars on demand visit our Webinars page


The Canadian Cancer Survivor Network is pleased to have Dr. Daniel Kopans from the Massachusetts General Hospital and Harvard Medical School present this webinar. In this session Dr. Kopans will discuss:

  1. The Canadian National Breast Screening Studies (CNBSS) are major outliers among the Randomized, Controlled Trials (RCT) of screening (which are the only way to prove that screening saves lives).  Contrary to the other RCTs which proved a benefit (lives saved) from screening women ages 40-74 (the ages of the women who participated) the CNBSS showed no benefit from screening for women at any age.
  2. From the beginning there have been questions about how the trial was performed.
    • Their own review showed that the quality of the mammography was “poor to unacceptable” for much of the trials.
    • They violated the fundamental rules for RCTs by examining all of the women prior to assigning them to the study arms, or the control arms, and then assigned women on open lists – another major violation.  This provided the opportunity to assign women out of random order and “load” the screening side with women with advanced cancers, biasing the results.
    • The data have always suggested an assignment imbalance.  A technologist in the trial recently confirmed that this happened.  By corrupting random assignment, the results of the CNBSS become unreliable.
  3. The results of the CNBSS should not be used to guide screening which has been proven to save lives for women ages 40-74.

To register for this Webinar click here.