The Radiation Studies Branch of the Centers for Disease Control and Prevention (CDC) charged the committee to address the following:
Are the study objectives attainable?
Are the proposed study design and the methods for data collection and statistical analyses unambiguous, and do they adequately address the study objectives? In particular, we would like the Committee to comment on the following:
The proposed expansion of the study cohort beyond the previous follow-up study of 1985-1986.
The adequacy of the proposed design in dealing with possible detection, selection, and information biases.
The appropriateness of the proposed outcome measures.
The approach for accounting for uncertainty and variability in individualized dose estimates and the dose-response analysis.
Has the statistical power of the study been appropriately addressed?
Present at the October 25, 2001 meeting, in addition to the members of the committee and the BRER staff, were representatives of the investigative team at the University of Utah, Joseph L. Lyon, the principal investigator; Wayne Meikle, the coinvestigator; Mary Bishop Stone, the program manager; Stephen Alder, the project’s statistician, and Owen Hoffman, who was recently hired as a consultant to the project, and Judy Qualters and Felix Rogers of CDC. Dr. Lyon and his colleagues described the proposed study and responded to the committee’s questions. The committee’s comments and recommendations set out in the paragraphs that follow stem from the written, albeit incomplete, documentation of the proposed research, the presentations, and responses to the committee’s queries. Our comments and recommendations are organized around the questions previously listed.
Question 1. Are the study objectives attainable?
The protocol is not sufficiently developed nor rigorous enough to permit a judgment of whether all the study objectives are attainable. Four objectives are stated:
“a. to test whether a healthy group of children, inadvertently exposed to radioactive iodine will have an increased number of thyroid neoplasms related to this exposure while controlling for other causes of thyroid cancer including medical x-rays and occupational radiation.”
Insufficient and incomplete information is presented in the protocol, and too few analyses have apparently been carried out, for the committee to judge the attainability of this objective in this cohort. In particular two elements necessary to ensure that the objective will be met were not adequately described in the protocol: safeguards in the study’s design, data collection and analysis to minimize the likelihood and magnitude of biases, and a correctly conceptualized method for determining the statistical power of the protocol and its application in the study design. Some examples of such issues are discussed in the committee's answer to question number 2 and in Appendix A.