PURPOSE: The PROPHET (Prostate Cancer: Prostate Health Index Trial) is a prospective study to clarify the diagnostic impact of laboratory based and prostate volume adjusted p2PSA ([-2] proenzyme prostate specific antigen) related indexes on prostate cancer and clinically significant prostate cancer with prostate specific antigen less than 10 ng/ml. MATERIALS AND METHODS: Between April 2015 and March 2017, 421 men 50 to 79 years old in the prostate specific antigen range above age specific cutoffs and below 10 ng/ml were registered in the PROPHET. We investigated the diagnostic impacts of various clinical laboratory based free prostate specific antigen related and p2PSA related indexes on any grade and high Gleason grade group prostate cancer. RESULTS: Of the 363 eligible participants 179, 141 and 80 were diagnosed with any grade, and Gleason Grade Group 2-5 and 3-5 prostate cancer, respectively. The AUC-ROCs distinguishing nonprostate cancer vs prostate cancer, nonprostate cancer plus low Gleason Grade Group and low volume vs remaining prostate cancer with a higher Gleason Grade group or a higher volume on the PHI (Prostate Health Index) were significantly superior to the AUC-ROCs of prostate specific antigen and free-to-total prostate specific antigen. At 90% sensitivity in all investigated p2PSA related indexes the false-positive rate was superior to that of prostate specific antigen and free-to-total prostate specific antigen in any group comparison in terms of the Gleason Grade Group and positive biopsy cores. In 35% to 42% of men without prostate cancer and/or those with less aggressive prostate cancer the PHI would avoid unnecessary biopsy. CONCLUSIONS: Laboratory based p2PSA related indexes were significantly superior for detecting clinically significant prostate cancer compared to free-to-total prostate specific antigen. The indexes those would avoid up to 42% of prostate biopsies in men without aggressive cancer while maintaining 90% sensitivity.
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