Moving a randomized clinical trial into an observational cohort

Area of Science:

• Oncology
• Preventive Medicine
• Clinical Trials

Background:

• The Selenium and Vitamin E Cancer Prevention Trial (SELECT) was a large-scale, randomized, double-blind, placebo-controlled study investigating prostate cancer prevention.
• Supplements (Vitamin E, Selenium) were discontinued due to lack of efficacy and futility analyses.
• The study transitioned to a Centralized Follow-Up (CFU) observational study to gather long-term data from the participant cohort.

Purpose of the Study:

• To describe the transition process from a randomized clinical trial to an observational Centralized Follow-Up (CFU) study.
• To outline the necessary changes at local study sites and the statistical center for central coordination.
• To maintain and follow the participant cohort for long-term biologic consequences of interventions.

Main Methods:

• Transition involved updating online documents, amending the protocol, reorganizing the statistical center, and revising data collection procedures.
• Procedures were developed for closing study sites and contacting participants for the CFU study.
• Participants were followed centrally via annual questionnaires and a web-based option.

Main Results:

• 17,761 participants were registered to the CFU study, fewer than anticipated due to IRB difficulties.
• An estimated 580 prostate cancer cases and 215 high-grade cancers are expected to be identified from this cohort.
• Over 109,000 mailings were sent to participants, and 12 biorepository proposals were approved.

Conclusions:

• The accrual goal for the CFU study was not met, limiting statistical power.
• Extended follow-up is crucial for understanding long-term intervention effects in prevention research.
• The CFU study provides a valuable, well-characterized cohort for collecting additional cancer endpoints and enhancing the utility of the SELECT biorepository.