The influence of unscheduled biopsies on prostate cancer detection in the Reduction by Dutasteride of Prostate Cancer Events (REDUCE) trial
Authors: Andriole G. L. , Pettaway C. , Tindall D. J. , Rittmaster R. S. , Wilson T. H. 
Published: August 2020

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Background: REDUCE is an ongoing 4-year, international, randomized, placebo-controlled study investigating the effect of dutasteride on the incidence of biopsy-detectable prostate cancer (PCa). We assessed the influence of prostate specific antigen (PSA)-driven, unscheduled biopsies on PCa detection. Methods: Eligible subjects were aged 50–75 years with serum PSA 2.5–10 ng/mL (50–60 years) or 3–10 ng/mL (>60 years) and a negative 6–12-core biopsy ≤6 months before enrollment. Protocol-mandated transrectal ultrasound directed biopsies (10 cores) were taken at 2 and 4 years; we report unblinded 2-year data. Results: Of the 8108 subjects in the efficacy population (subjects with no PCa in baseline biopsy as assessed by Central lab and who took at least one dose of study medication), 356 subjects (4.4%) underwent an unscheduled biopsy (0–18 months), and 6460 subjects (79.7%) underwent a protocol-mandated (scheduled) biopsy (19–24 months). Rising PSA was the primary reason for an unscheduled biopsy. PCa was diagnosed in 60 subjects (16.9%) at an unscheduled biopsy compared with 950 subjects (14.7%) at scheduled biopsy. Subjects with PCa on unscheduled, compared with scheduled, biopsy had higher baseline PSA (6.63 vs. 6.06 ng/mL), lower % free PSA (13.2% vs. 15.5%); there was no difference in the mean number of baseline biopsy cores (8.6 vs. 8.4). Conclusions: Although unscheduled biopsies in REDUCE were slightly more likely to result in a cancer diagnosis and have a higher Gleason score, the small number of such biopsies (356/6591, 5.4% of subjects biopsied) would not cause a significant ascertainment bias. This contrasts the prostate cancer prevention trial (PCPT), where close to 40% of subjects had for-cause biopsies (most often PSA-driven), creating a substantial detection bias for high-grade cancers.

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