Appendix 1: Terms of reference for the review of the randomization procedures of the Canadian National Breast Screening Study

The following terms of reference are taken from a letter to the reviewers dated Mar. 30, 1995, from Dr. J. David Beatty, then executive director of the National Cancer Institute of Canada.

1. Review the randomization strategy, in the context of when the study was planned (1976), the size of the study, and the randomization strategies of other similar studies.

2. Review the original randomization sheets for evidence of possible randomization violations, such as overwritten names, erasures, unused slots, etc.

3. For each if the 24 subjects with breast cancer at the original screen who had four or more nodes positive, review the records for randomization violations (e.g., check the times of their original examination and when they were randomized).

4. At the centres in which substantial differences in breast cancer mortality are present between the mammography and usual-care groups, review the records for randomization violations of each of the women who had physical abnormalities at initial screen, who were referred to review and in whom cancer was detected by the screening process.

5. Contact an individual who was reported to have claimed to have first-hand information concerning compromise of the randomization process to obtain information about this matter.