Serum pro-prostate specific antigen preferentially detects aggressive prostate cancers in men with 2 to 4 ng/ml prostate specific antigen

Purpose: Pro forms of prostate specific antigen (PSA) have been reported to be more cancer specific markers of prostate cancer than total PSA and they also may preferentially detect the more aggressive forms of the disease. Materials and Methods: Research immunoassays with high specificity for pro-PSA forms were used to study 1,091 retrospective serum specimens, including 555 with 2 to 4 and 536 with 4 to 10 ng/ml PSA, from men enrolled in prostate cancer screening studies who underwent prostate biopsy. Results: In the 2 to 4 ng/ml PSA range the ratio of pro- to free-PSA (percent pro-PSA) using a cutoff of 1.8% for recommending prostate biopsy detected 90% of cancers, including 16 of 16 extracapsular tumors and 28 of 29 tumors with a pathology Gleason score of 7 or greater, while avoiding 19% of unnecessary biopsies. Serum percent pro-PSA was significantly increased for Gleason score 7 or greater vs less than 7 (p = 0.0018). In the PSA range of 4 to 10 ng/ml percent pro-PSA had the highest cancer specificity, avoiding 31% of unnecessary biopsies, while detecting 34 of 35 cancers with a pathology Gleason score of 7 or greater and 29 of 31 extracapsular tumors. Neither percent free PSA nor complexed PSA enhanced the detection of aggressive cancers in the 4 to 10 ng/ml PSA range. Conclusions: Percent pro-PSA was superior to percent free and calculated complexed PSA for the detection of prostate cancer in the PSA range of 2 to 10 ng/ml and it had selectivity for detecting more aggressive cancers, as indicated by Gleason score 7 or greater and/or extracapsular tumor extension.