Background
The Prostate Cancer Prevention Trial (PCPT) was a 7-year randomized, double-blind, placebo-controlled trial of the efficacy of finasteride for the prevention of prostate cancer with a primary outcome of histologically-determined prevalence of prostate cancer at the end of 7 years.
Methods
A systematic modeling process using logistic regression identified factors available at year 6 that are associated with end-of-study (EOS) biopsy adherence at year 7, stratified by whether participants were ever prompted for a prostate biopsy by year 6. Final models were evaluated for discrimination. At year 6, 13,590 men were available for analysis.
Results
Participants were more likely to have the EOS biopsy if they were adherent to study visit schedules and procedures and/or were in good health (p<.01). Participants at larger sites and/or sites that received retention and adherence grants were also more likely to have the EOS biopsy (p<.05).
Conclusions
Our results show good adherence to study requirements one year prior to the EOS biopsy was associated with greater odds that a participant would comply with the invasive EOS requirement.
Impact
Monitoring adherence behaviors may identify participants at risk of non-adherence to more demanding study end points. Such information could help frame adherence intervention strategies in future trials.