Methods and Applications of Statistics in Clinical Trials, Volume 2: Planning, Analysis, and Inferential Methods

Chapter 44

Screening Trials

Philip C. Prorok

44.1 Introduction

The early detection of cancer and other chronic diseases has long been a goal of medical scientists. Many believe that by moving the point of diagnosis backward in time so that the disease is diagnosed earlier than usual, treatment will be more effective than treatment given at the usual time. However, this presumption may not be correct, and the effect of any screening program must be evaluated. Cohort studies and case–control studies have been used for evaluating screening for several types of cancer, and the design and interpretation of these studies have recently been the topic of increasing discussion. However, an observational study rarely yields definitive answers or permits solid conclusions with regard to the public health consequences of cancer screening. The most rigorous approach is the randomized clinical trial. There are special design and analysis issues for such screening trials.

44.2 Design Issues

The randomized controlled trial involves the prospective testing and long-term follow-up of defined populations according to a protocol. There are several major design and implementation aspects that should be considered. First, the target disease(s), the screening test(s), and the diagnostic and therapeutic regimens must be determined. Then, the appropriate outcome variable must be chosen and the sampling unit (individual or group) selected. Next, the admission and exclusion criteria need to be established ...