Predictors of participant retention in two chemoprevention feasibility trials

Retention of participants for intervention and follow-lip activities is cri tical in cancer chemoprevention trials. Little has been published about ret ention patterns and predictors of retention in prevention studies. The Caro tene and Retinol Efficacy Trial (CARET) provides an opportunity to study re tention of volunteer participants in a large, long-term clinical trial. Two pilot studies were conducted in different populations to test the feasibil ity of critical strategies for the long-term study. Thirteen pel cent of th e asbestos-exposed workers and 18% of the smokers became inactive during th e pilot study! Of those remaining active, all bur 2% of asbestos-exposed wo rkers pilot study participants and 5% of smokers pilot study participants c hose to participate in the full-scale efficacy trial. Five baseline predict ors of inactivity for the asbestos-exposed participants emerged: being non- White, being a current smoker; having a history of high blood pressure at b aseline,,reporting two or more increases in symptoms during the placebo run -in, and having higher baseline levels of negative mental health measures ( i.e. anxiety, depression, and fatigue). The only significant predictor of i nactivity for smoker pilot participants was reporting symptoms during the p lacebo run-in. The most frequently reported reasons for becoming inactive d uring the pilot studies were general health issues and problems and symptom s that were seen as specific to the CARET vitamins. These findings suggest areas that could be tested to optimize retention in clinical trials.