title: Impact of multiparametric endorectal coil prostate magnetic resonance imaging on disease reclassification among active surveillance candidates: a prospective cohort study.
abstract: OBJECTIVE
  We report magnetic resonance imaging findings among unselected men with low risk prostate cancer before active surveillance.
  
  
  METHODS
  We prospectively enrolled men with low grade, low risk, localized prostate cancer. All patients underwent multiparametric endorectal coil magnetic resonance imaging and were offered confirmatory biopsy within 1 year of imaging. The primary outcome was the impact of magnetic resonance imaging on identifying patients who were reclassified by confirmatory biopsy as no longer fulfilling active surveillance criteria. We further identified clinical parameters associated with reclassification. The cohort was stratified as patients with 1) normal magnetic resonance imaging, 2) cancer on magnetic resonance imaging concordant with initial biopsy (less than 1 cm) and 3) cancer on magnetic resonance imaging larger than 1 cm. We performed univariate analysis to assess differences in clinical parameters among the groups.
  
  
  RESULTS
  Magnetic resonance imaging did not detect cancer in 23 cases (38%) while magnetic resonance imaging and initial biopsy were concordant in 24 (40%). Magnetic resonance imaging detected a 1 cm or larger lesion in 13 patients (22%). Of the cases 18 (32.14%) were reclassified. When no cancer was identified on magnetic resonance imaging, only 2 cases (3.5%) were reclassified. The positive and negative predictive values for magnetic resonance imaging predicting reclassification were 83% (95% CI 73-93) and 81% (95% CI 71-91), respectively. Prostate specific antigen density was increased in patients with lesions larger than 1 cm on magnetic resonance imaging compared to those with no cancer on imaging (median 0.15 vs 0.07 ng/ml/cc, p=0.016).
  
  
  CONCLUSIONS
  Magnetic resonance imaging appears to have a high yield for predicting reclassification among men who elect active surveillance. Upon confirmation of our results magnetic resonance imaging may be used to better select and guide patients before active surveillance.
authors.affiliation: Division of Urology, Department of Surgical Oncology, Princess Margaret Hospital, University Health Network, Toronto, Ontario, Canada. sdmargel@gmail.com
authors.forename: David
authors.initials: D
authors.lastname: Margel
authors.forename: Stanley A
authors.initials: SA
authors.lastname: Yap
authors.forename: Nathan
authors.initials: N
authors.lastname: Lawrentschuk
authors.forename: Laurence
authors.initials: L
authors.lastname: Klotz
authors.forename: Masoom
authors.initials: M
authors.lastname: Haider
authors.forename: Karen
authors.initials: K
authors.lastname: Hersey
authors.forename: Antonio
authors.initials: A
authors.lastname: Finelli
authors.forename: Alexandre
authors.initials: A
authors.lastname: Zlotta
authors.forename: John
authors.initials: J
authors.lastname: Trachtenberg
authors.forename: Neil
authors.initials: N
authors.lastname: Fleshner
mesh_terms: D015331:Cohort Studies; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D011159:Population Surveillance; D011446:Prospective Studies; D011471:Prostatic Neoplasms / Q000145:classification* / Q000175:diagnosis*