Factors Associated with Adherence to an End-of-Study Biopsy: Lessons from the Prostate Cancer Prevention Trial (SWOG-Coordinated Intergroup Study S9217)

Abstract

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.

Baseline subject characteristics predictive of compliance with study-mandated prostate biopsy in men at risk of prostate cancer: results from REDUCE

“…(5) However, this number does not include the additional 8% who were lost to follow-up or died prior to year-6. Together with our data, non-compliance with study-mandated prostate biopsy may range from 22%-45%.…”

“…(5) We did not examine on-study medication adherence predicting biopsy compliance because we sought to test only baseline factors predicting the 2-year biopsy. However, we did find biopsy compliance was similar in dutasteride vs. placebo arms.…”

“…The only other study examining compliance with study-mandated prostate biopsy in a clinical trial is from PCPT where among men with 6-year data, 37% did not undergo the year-7 end-of-study biopsy. ( 5 ) However, this number does not include the additional 8% who were lost to follow-up or died prior to year-6. Together with our data, non-compliance with study-mandated prostate biopsy may range from 22%-45%.…”

“…In PCPT, study drug (finasteride) adherence at year-6 was associated with 84% compliance with year-7 biopsy vs. 47% for those who were non-adherent to study drug at year-6 (p<0.0001). ( 5 ) We did not examine on-study medication adherence predicting biopsy compliance because we sought to test only baseline factors predicting the 2-year biopsy. However, we did find biopsy compliance was similar in dutasteride vs. placebo arms.…”

“…Factors predictive of biopsy compliance included compliance with on-study medical therapy a year prior, age <70, and never smoking. ( 5 ) However, this study examined factors at year-6 predicting compliance with the year-7 procedure, rather than baseline characteristics. Additionally, this trial was performed only in the U.S. and did not include men from other geographic regions.…”