Healthy men participating in the Prostate Cancer Prevention Trial who actively participate in all steps of the clinical trial are most likely to undergo a biopsy at the end of the trial, according to a new study.

The Prostate Cancer Prevention Trial is a randomized, double-blind, placebo-controlled trial that tested the efficacy of finasteride, a drug used for prostate cancer prevention. This study was conducted by SWOG—a cancer research cooperative group that designs and conducts multidisciplinary clinical trials.

Researchers at The University of Texas MD Anderson Cancer Center in Houston, Texas, and the Fred Hutchinson Cancer Research Center in Seattle, Washington, used a systematic model to identify factors associated with men adhering to the end-of-study (EOS) biopsy requirement of the trial. The EOS biopsy is an important part of the study.

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“Our study is unique because it evaluated factors prospectively associated with an invasive biopsy for a cancer prevention trial, not a cancer treatment trial,” said lead author Ellen R. Gritz, PhD, chair of Behavioral Science at MD Anderson. This study was published in Cancer Epidemiology, Biomarkers and Prevention (2014; doi:10.1158/1055-9965.EPI-14-0202).

The prevention trial was coordinated by SWOG at 219 sites involving more than 18,000 men. Participants were randomized into 1 of 2 groups; those administered finasteride and those given a placebo. Participants received educational materials about the study and biopsy procedures and were asked to attend regularly scheduled appointments throughout the trial.

Funded by the National Cancer Institute, scientists analyzed healthy men over a 7-year period to identify which factors at the 6-year study mark were associated with the willingness of the participant to undergo a biopsy. The factors examined included psychosocial outcomes, participant health status, participant adherence, and characteristics of the clinical sites at which the study was conducted.

“The biopsy provided the biological specimens that could be tested to see if a man’s prostate cells were cancer-free after 7 years on the trial,” said Carol Moinpour, PhD, of the Fred Hutchinson Cancer Research Center. “That is, the biopsy provided definitive information about which men had prostate cancer 7 years after the study started.”

Researchers found participants were more likely to adhere to the EOS biopsy criteria if at 1 year prior to the biopsy they were adherent to the study drug, kept appointments and underwent required tests, and were in good health. Participants who underwent an EOS biopsy were more likely to be adherent to the study drug at year 6, as 84% were adherent. Among participants who did not undergo biopsy, only 47% were adherent to the study drug. Results also showed that 98% of men who underwent an EOS biopsy also underwent digital rectal examination (DRE) or PSA test at year 6, compared with 75% of men who did not undergo the EOS biopsy.