Predictors of participant retention in two chemoprevention feasibility trials

Our plain-English summary of Predictors of participant retention in two chemoprevention feasibility trials, by D.J. Bowen, B. Cartmel, M. Barnett, et al (Annals of Behavioral Medicine, 1999).

The study

• Authors: D.J. Bowen, B. Cartmel, M. Barnett, G. Goodman, G.S. Omenn
• Journal: Annals of Behavioral Medicine
• Published: 1999;21(3):210-5
• Type of article: Randomized trial
• Cited by: 8 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Retention of participants for intervention and follow-up activities is critical in cancer chemoprevention trials. Little has been published about retention patterns and predictors of retention in prevention studies. The Carotene and Retinol Efficacy Trial (CARET) provides an opportunity to study retention of volunteer participants in a large, long-term clinical trial. Two pilot studies were conducted in different populations to test the feasibility of critical strategies for the long-term study. Thirteen percent of the asbestos-exposed workers and 18% of the smokers became inactive during the pilot study. Of those remaining active, all but 2% of asbestos-exposed workers pilot study participants and 5% of smokers pilot study participants chose to participate in the full-scale efficacy trial. Five baseline predictors of inactivity for the asbestos-exposed participants emerged: being non-White, being a current smoker, having a history of high blood pressure at baseline, 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 inactivity for smoker pilot participants was reporting symptoms during the placebo run-in. The most frequently reported reasons for becoming inactive during the pilot studies were general health issues and problems and symptoms that were seen as specific to the CARET vitamins. These findings suggest areas that could be tested to optimize retention in clinical trials.

In plain English

This article examined retention in two pilot trials run before the Carotene and Retinol Efficacy Trial (CARET), a lung cancer prevention trial, and what predicted becoming inactive. One pilot randomized 816 men with occupational asbestos exposure to 15 mg beta-carotene plus 25,000 IU retinol or placebo. The other randomized 1,029 heavy smokers. During the pilots, 13% of the asbestos-exposed workers and 18% of the smokers became inactive. Among asbestos-exposed workers, a history of high blood pressure (risk ratio 1.70, 95% confidence interval 1.12-2.60) and a higher combined baseline anxiety, depression and fatigue score (1.12 per one-unit increase, 1.01-1.24) predicted inactivity. Being non-White, being a current smoker, and reporting increases in two or more symptoms during a placebo run-in approached significance. Among smokers, only run-in symptoms predicted inactivity (risk ratio 1.69, 1.11-2.56). Across both pilots, current smokers and those on the study for less time were less likely to move into the full trial. The most common reasons for becoming inactive during the pilots were general health issues, monitored symptoms, and study center location and transportation. The authors concluded that the findings suggest retention methods needing rigorous evaluation.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Analysis of participant retention in two randomized, placebo-controlled pilot (feasibility) trials for CARET. Cox proportional hazards regression was used for inactivity during the pilots, and logistic regression for inactivity during the transition to the full-scale trial.
• Who was studied: 1,845 randomized pilot participants in the U.S. The Asbestos-Exposed Workers Pilot had 816 men aged 45-74, recruited June 1985 through July 1988. The Smokers Pilot had 1,029 men and women aged 50-69 with at least 20 pack-years of smoking, recruited June 1985 through December 1987. After exclusions, the analyses included 789 asbestos-exposed participants and 970 smokers.
• Exposure: Asbestos-exposed participants had occupational asbestos exposure that began at least 15 years before entry. They also had either a chest x-ray consistent with asbestos-related fibrosis of the lung tissue or pleura, or 5 years of work in one of eight specified high-risk trades. No fiber type is named. The trial intervention in this pilot was 15 mg beta-carotene plus 25,000 IU retinol versus placebo. The factors analyzed as predictors of retention were baseline characteristics: race, smoking, Karnofsky score, medication, family cancer history, high blood pressure, multivitamin use, run-in symptoms, age, and a mental health score.
• Main results:
  • During the pilot studies, 13% of asbestos-exposed participants and 18% of smoker participants became inactive. Inactive participants no longer took part in the intervention but were still followed on a reduced contact schedule.
  • Of those who stayed active through the pilot, all but 2% of asbestos-exposed participants and all but 5% of smoker participants chose to join the efficacy trial.
  • Among asbestos-exposed participants (N = 789; 99 became inactive), a history of high blood pressure predicted inactivity: risk ratio 1.70, 95% confidence limits 1.12-2.60, significance 0.01.
  • Among asbestos-exposed participants, a higher baseline mental health score predicted inactivity. This was a continuous score combining anxiety, depression and fatigue. The risk ratio was 1.12 per one-unit increase in the score, with 95% confidence limits 1.01-1.24 and significance 0.03.
  • Among asbestos-exposed participants, being non-White (significance 0.07), being a current smoker (0.10) and run-in symptoms (0.08) were described with blood pressure and mental health as predictors that 'reach or approach significance'. Age and familial cancer history were not significant predictors.
  • Among smoker participants (N = 970; 180 became inactive), the only significant predictor of inactivity was reporting symptoms during the placebo run-in: risk ratio 1.69, 95% confidence limits 1.11-2.56, significance 0.02.
  • High blood pressure was associated with inactivation in the asbestos-exposed group but with retention in smokers. In smokers this result was not significant (risk ratio 0.75, 0.53-1.08).
  • In the combined analysis of the transition to the full trial (N = 825; 54 became inactive), two factors predicted not making the transition. Current smokers were less likely to make it (risk ratio 2.22, 1.13-4.36, significance 0.02). Those on the study for less time were also less likely (risk ratio 0.96, 0.93-1.00, significance 0.04).
  • General health issues were the most common reason given for becoming inactive during the pilots (42% of asbestos-exposed and 53% of smoker participants). Monitored symptoms were next (18% and 29%), then location and transportation (11% and 14%). Participants could give more than one reason.
• The authors' conclusion: The authors concluded that the findings suggest additional methods for improving retention in clinical trials, but that these methods should be rigorously evaluated. One example is screening participants who report run-in symptoms before randomization.
• Limitations the authors state:
  • There were few asbestos-exposed inactivations during the transition period, so only one combined model was fit for both pilot populations.
  • The inactivation date was usually the day the study center was notified, so participants may have stopped taking the capsules earlier.
  • The authors stated that the findings must be replicated in real-world clinical settings.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Lung cancer.

Medical terms in this study, explained in our Lexicon: Clinical Trial.

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