title: Evidence for a biopsy derived grade artifact among larger prostate glands.
abstract: OBJECTIVE
  The PCPT has demonstrated a higher incidence of high grade (Gleason pattern 4 or greater) prostate cancers among men randomized to finasteride. One plausible explanation for this finding is that tumor grade as assigned by TRUS guided biopsy is artifactually associated with prostate volume.
  
  
  METHODS
  We evaluated our institutional data set of TRUS guided biopsies in the last 3 years and identified 369 cases of prostate cancer that fit the criteria of PSA less than 10 ng/ml, biopsy at our center and RP at our center. We identified risk factors for Gleason pattern 4 or greater on biopsy and then on RP specimens from the same patients using univariate and multiple logistic regression analyses. Assessed covariates included patient age, PSA and TRUS volume.
  
  
  RESULTS
  Risk factors for Gleason pattern 4 or greater in the biopsy specimens included age (p = 0.01), hypoechoic lesions on TRUS (p <0.001) and TRUS volume (p = 0.008). However, among RP specimens TRUS volume (p = 0.60) became nonsignificant of Gleason pattern 4 or greater on multivariable analysis. Although prostate volume was a predictor for biopsy derived high grade disease it was not predictive of true histological grade.
  
  
  CONCLUSIONS
  These data suggest that simply having a larger prostate results in fewer high grade cancers diagnosed at biopsy. Prostatectomy results in the same men suggest sampling artifact, as the distribution of cancer grade is not associated with prostate volume. These findings provide evidence that the increase in higher grade tumors among men in the finasteride arm of PCPT may simply result from prostate volume reduction.
authors.affiliation: Division of Urology, Princess Margaret Hospital, University of Toronto, Toronto, Canada.
authors.forename: Girish S
authors.initials: GS
authors.lastname: Kulkarni
authors.forename: Rami
authors.initials: R
authors.lastname: Al-Azab
authors.forename: Gina
authors.initials: G
authors.lastname: Lockwood
authors.forename: Ants
authors.initials: A
authors.lastname: Toi
authors.forename: Andrew
authors.initials: A
authors.lastname: Evans
authors.forename: John
authors.initials: J
authors.lastname: Trachtenberg
authors.forename: Michael A S
authors.initials: MA
authors.lastname: Jewett
authors.forename: Antonio
authors.initials: A
authors.lastname: Finelli
authors.forename: Neil E
authors.initials: NE
authors.lastname: Fleshner
mesh_terms: D000328:Adult; D000368:Aged; D016477:Artifacts; D001706:Biopsy; D006801:Humans; D008297:Male; D008875:Middle Aged; D011467:Prostate / Q000473:pathology*; D012189:Retrospective Studies