Predictors of inactivation and reasons for participant inactivation duringa skin cancer chemoprevention study

Maintaining good compliance is a major challenge in long-term cancer chemop revention trials. Minimizing the number of inactive participants during a t rial is an important factor in maximizing compliance. Identifying reasons f or and predictors of inactivation is the first step in being able to reduce participant inactivation, In this skin cancer chemoprevention trial, the 2 ,297 participants were randomized to receive 25,000 IU of retinol daily or a placebo. Median follow-up time was 3.8 years. The reason for inactivation was determined for each participant who stopped taking the study capsules. Six hundred and seventy-seven (29.7%) participants became inactive during the 5-year study. There was no significant difference between the number of participants inactivating by treatment group or sex. The most common reaso ns for inactivation were illness of subject, spouse, or a close relative (1 8.6%) and experience of a clinical symptom consistent with vitamin A ingest ion (17.1%). Participants in the vitamin A group (10.1%) more frequently ci ted symptoms coded as "not consistent with vitamin A" as the reason for ina ctivation compared with those in the placebo group [5.4% (P < 0.05)], The i nactivation rate was highest in the first month of the trial acid declined thereafter. A low education level (hazard ratio, 1.59) and unmarried status (hazard ratio, 1.29) were the only significant predictors of inactivation. These findings may be useful in developing targeted strategies to decrease inactivation and thereby increase compliance in future chemoprevention tri als. However, these Findings need to be confirmed because published researc h in this area is very limited.