title: Low percentage of free prostate-specific antigen (PSA) is a strong predictor of later detection of prostate cancer among Japanese men with serum levels of total PSA of 4.0 ng/mL or less.
abstract: OBJECTIVE
  To investigate the effect of the percentage of free prostate-specific antigen (%fPSA) on future prostate cancer risk.
  
  
  METHODS
  We examined serum total PSA (tPSA) and %fPSA annually in a prostate cancer-screening cohort between July 2001 and June 2011. Men with tPSA >4.0 ng/mL or tPSA of 2.0-4.0 ng/mL with %fPSA ≤12% were screened as positive and were recommended to undergo a biopsy. The study population consisted of 6368 men, aged 40-79 years, who had tPSA ≤4.0 ng/mL at initial screening and who subsequently underwent 1 or more screenings. We calculated the cumulative risk and hazard ratio of prostate cancer stratified by the initial %fPSA groups as quartiles of prostate cancer patients.
  
  
  RESULTS
  During a median follow-up of 36 months, 119 men were diagnosed with prostate cancer. The lowest quartile of %fPSA (<13.3%) was associated with a 21.2-fold higher risk of having prostate cancer compared with the highest quartile (>22.2%). For the subset with an initial tPSA ≤1.0 ng/mL, all men diagnosed with cancer had an initial %fPSA ≤33.3% (median). For the subset with tPSA >1.0 ng/mL, men with %fPSA ≤23.0% (median) had significantly higher risk for cancer than those with %fPSA >23.0% (P <.0001). Of the 114 men with prostate cancer in whom pathologic findings were available, 79 (69.3%) had a Gleason score ≥3 + 4 = 7.
  
  
  CONCLUSIONS
  A low %fPSA is a strong predictor of a subsequent diagnosis of prostate cancer among men with tPSA levels ≤4.0 ng/mL. Measurement of %fPSA might enhance the detection of high-grade cancer that warrants aggressive treatment.
authors.affiliation: Department of Urology, Tohoku University Graduate School of Medicine, Sendai, Japan. Electronic address: mitsuharu@uro.med.tohoku.ac.jp.
authors.forename: Mitsuharu
authors.initials: M
authors.lastname: Sasaki
authors.affiliation: Department of Urology, Sendai City Hospital, Sendai, Japan.
authors.forename: Shigeto
authors.initials: S
authors.lastname: Ishidoya
authors.affiliation: Department of Urology, Tohoku University Graduate School of Medicine, Sendai, Japan.
authors.forename: Akihiro
authors.initials: A
authors.lastname: Ito
authors.affiliation: Department of Urology, Tohoku University Graduate School of Medicine, Sendai, Japan.
authors.forename: Hideo
authors.initials: H
authors.lastname: Saito
authors.affiliation: Department of Urology, Tohoku University Graduate School of Medicine, Sendai, Japan.
authors.forename: Shigeyuki
authors.initials: S
authors.lastname: Yamada
authors.affiliation: Department of Urology, Tohoku University Graduate School of Medicine, Sendai, Japan.
authors.forename: Koji
authors.initials: K
authors.lastname: Mitsuzuka
authors.affiliation: Department of Urology, Tohoku University Graduate School of Medicine, Sendai, Japan.
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Kaiho
authors.affiliation: Miyagi Cancer Society, Sendai, Japan.
authors.forename: Daisuke
authors.initials: D
authors.lastname: Shibuya
authors.affiliation: Division of Biostatistics, Tohoku University Graduate School of Medicine, Sendai, Japan.
authors.forename: Takuhiro
authors.initials: T
authors.lastname: Yamaguchi
authors.affiliation: Department of Urology, Tohoku University Graduate School of Medicine, Sendai, Japan.
authors.forename: Yoichi
authors.initials: Y
authors.lastname: Arai
mesh_terms: D000328:Adult; D000368:Aged; D044466:Asian People; D001706:Biopsy; D055088:Early Detection of Cancer / Q000379:methods; D006801:Humans; D007564:Japan; D008297:Male; D008875:Middle Aged; D016016:Proportional Hazards Models; D017430:Prostate-Specific Antigen / Q000097:blood*; D011471:Prostatic Neoplasms / Q000097:blood* / Q000175:diagnosis / Q000208:ethnology; D016896:Treatment Outcome
chemical_list: D017430:Prostate-Specific Antigen