Behavioral aspects of clinical trials. An integrated framework from behavior theory.

A less-than-optimal proportion of patients with cancer are entered into National Cancer Institute-sponsored clinical trials. This article reviews the literature on accrual in oncology clinical trials to characterize the extent of the problem, identify reasons for low accrual, and suggest ways to promote accrual. Four well known theories of health behavior (the Health Belief Model, Subjective Expected Utility Theory, Protection Motivation Theory, and the Theory of Reasoned Action) point to central concepts involved in understanding patient health-related behavior: (1) the probability that an unwelcomed health event will happen to a patient, (2) the severity of that event if it does occur, (3) the effectiveness of a particular behavior (such as taking part in a clinical trial) to modify the severity, and (4) the cost of adopting that behavior. These concepts form a framework for integrating the available information about accrual to clinical oncology trials. Patient and physician factors previously related to clinical trials suggest specific recommendations for increasing accrual to clinical oncology trials.