title: Predictors of prostate cancer evaluated by receiver operating characteristics partial area index: a prospective institutional study.
abstract: OBJECTIVE
  To our knowledge we introduce the ROC partial area under the curve (AUC) index as a method of evaluating the discriminative power of different prostate cancer predictors. Peripheral zone volume and peripheral zone prostate specific antigen (PSA) density are introduced as potential predictors and compared with other known predictors of prostate cancer.
  
  
  METHODS
  During 1999, 220 consecutive patients with suspected early prostate cancer were examined using total PSA, free PSA, total prostate volume, transition zone volume and transrectal ultrasonography guided sextant biopsy of the prostate. The free-to-total PSA ratio, PSA density, transition zone PSA density, peripheral zone volume and peripheral zone PSA density were calculated. Usually total AUC is used to evaluate the discriminative power of different parameters. In this study parameters were evaluated by the ROC partial area index, which includes only the AUC in highly sensitivity parts of the ROC curve. Explorative analysis using logistic regression analysis was performed to investigate the ability of combinations of parameters to predict cancer.
  
  
  RESULTS
  Of the 220 patients 75 were diagnosed with cancer. In the subgroup of 160 patients with PSA less than 10 microg/l 44 had cancer. Transition zone PSA density and PSA density had significant discriminative power in the total group, while none of the parameters were discriminative in the subgroup of patients.
  
  
  CONCLUSIONS
  When high sensitivity is demanded, the ROC partial area index seems to be meaningful for evaluating the discriminative power of potential predictors. In our study none of the evaluated parameters had discriminative power in patients with PSA less than 10 microg/l, while transition zone PSA density and PSA density showed discriminative power in the total group of patients.
authors.affiliation: Section of Urology, Department of Surgery, Haukeland University Hospital, Bergen, Norway.
authors.forename: Peder
authors.initials: P
authors.lastname: Gjengstø
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Paus
authors.forename: Ole Johan
authors.initials: OJ
authors.lastname: Halvorsen
authors.forename: Johan
authors.initials: J
authors.lastname: Eide
authors.forename: Lars Andreas
authors.initials: LA
authors.lastname: Akslen
authors.forename: Tore
authors.initials: T
authors.lastname: Wentzel-Larsen
authors.forename: Per Aage
authors.initials: PA
authors.lastname: Hoisaeter
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D006801:Humans; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D011446:Prospective Studies; D011471:Prostatic Neoplasms / Q000175:diagnosis*; D012372:ROC Curve; D012680:Sensitivity and Specificity