Some challenges in evaluating prostate screening: subjective adjudication of outcomes, and over-diagnosis

Thursday, 13 April 2017
12 noon - 1.00pm
Melbourne University, Old Geology Lecture Theatre 1
Grattan Street

This seminar is presented in conjunction with the School of Mathematics and Statistics, University of Melbourne

The European Randomised Study of Prostate Cancer Screening has shown a substantial reduction in prostate cancer mortality, but a similar trial in the United States showed essentially no benefit. Because there is no “gold standard” for causes of death, we analysed the European data to find out if uncertainty in identifying prostate cancer deaths might have affected the results. Several latent class models were formulated to estimate the accuracy of outcome adjudicators and to determine if their accuracy varied, and ultimately to assess if adjudication errors rates might be differential between the study arms – and hence represent a potential bias.

The analysis revealed some discrepancies between adjudicators, but there was only limited evidence of asymmetry between them. There was no consistent evidence of differential accuracy by trial arm. We made corrections to the study results to allow for adjudication errors, but we concluded that bias arising from this issue was unlikely. Hence, other factors are probably responsible for the difference between the European and US findings.

In general terms, this analysis represents an interesting example of how one can assess potential bias in trial results when determination of the study end point is uncertain.

If time allows, we may also briefly discuss ongoing work on how to estimate the extent of overdiagnosis occurring in prostate screening.

Professor Stephen Walter

Prof. Stephen Walter

McMaster University

Stephen Walter, Professor Emeritus, received his Ph.D. from the University of Edinburgh. After faculty appointments at the University of Ottawa and Yale University, he joined the Department of Clinical Epidemiology and Biostatistics at McMaster University. Dr. Walter has collaborated in research on medical screening and diagnosis, internal medicine, evidence-based medicine, developmental paediatrics, environmental health, and cancer etiology. He is interested in biostatistical methodology, including: the design and analysis of medical research studies; risk assessment; evaluation of diagnostic and screening tests; and regional and temporal variation in health. He has published widely on these topics (with almost 500 refereed papers) in the biomedical and statistical literature.

Dr Walter is a past Editor of the American Journal of Epidemiology, and Section Editor for the Wiley Encyclopedia of Biostatistics. He served as Chair of Biostatistics in the International Clinical Epidemiology Network (INCLEN), and has been involved with research capacity development in Asia, Latin America and Africa. Dr Walter is a Visiting Professor in Australia and Finland, and he has been involved in research activities in several other countries. He is a past coordinator of the Health Research Methods program at McMaster, and has worked with about 100 Masters and Ph.D. students.