title: Are magnetic resonance imaging undetectable prostate tumours clinically significant? Results of histopathological analyses.
abstract: OBJECTIVE
  To investigate whether tumours at threshold values for detection on magnetic resonance imaging (MRI) represent clinically significant tumours or not, and therefore the utility of MRI in active surveillance (AS) protocols.
  
  
  METHODS
  A retrospective analysis of a single institution database was performed after Institutional Review Board approval. Between 2010 and 2013, 1633 patients underwent robot-assisted laparoscopic prostatectomy (RALP) at a single institution by a single surgeon. Of these, 1361 had complete clinical data and were included in analysis. Multivariate logistic regression was used to assess histopathological grade compared to tumour size whilst controlling for biopsy Gleason score, prostate-specific antigen level, body mass index, race, and age.
  
  
  RESULTS
  Of 120 tumours <5 mm in size, four were Gleason score 4 + 3. Of 276 tumours of 5-10 mm, 22 (8.1%) were Gleason score 4 + 3 and one (0.2%) was Gleason score 8. On multivariate regression analyses, tumours of <5 mm were much less likely to be high grade (Gleason score >3 + 4) at RALP compared to larger tumours (3.3% vs 25.1%,P< 0.001), or Gleason score ⩾8 (0.0% vs 7.6%,P< 0.001). Size was further shown to significantly correlate with grade on multivariate regression (P< 0.001).
  
  
  CONCLUSIONS
  Prostate tumours below the detection threshold for MRI (5 mm) most probably represent clinically insignificant tumours, which alone would not necessitate leaving AS in favour of more aggressive therapy. These findings point to a possible role of MRI in modern AS protocols.
authors.affiliation: Department of Urology, Mount Sinai Medical Center, New York, NY, USA.
authors.forename: Kristian D
authors.initials: KD
authors.lastname: Stensland
authors.affiliation: Department of Urology, Mount Sinai Medical Center, New York, NY, USA.
authors.forename: Karl
authors.initials: K
authors.lastname: Coutinho
authors.affiliation: Department of Urology, Mount Sinai Medical Center, New York, NY, USA.
authors.forename: Adele R
authors.initials: AR
authors.lastname: Hobbs
authors.affiliation: Department of Urology, Mount Sinai Medical Center, New York, NY, USA.
authors.forename: Lindsay
authors.initials: L
authors.lastname: Haines
authors.affiliation: Department of Urology, Mount Sinai Medical Center, New York, NY, USA.
authors.forename: Shemille A
authors.initials: SA
authors.lastname: Collingwood
authors.affiliation: Department of Urology, Mount Sinai Medical Center, New York, NY, USA.
authors.forename: Young Suk
authors.initials: YS
authors.lastname: Kwon
authors.affiliation: Department of Urology, Mount Sinai Medical Center, New York, NY, USA.
authors.forename: Simon J
authors.initials: SJ
authors.lastname: Hall
authors.affiliation: Department of Urology, Mount Sinai Medical Center, New York, NY, USA.
authors.forename: Maria
authors.initials: M
authors.lastname: Katsigeorgis
authors.affiliation: Department of Urology, Lenox Hill Hospital, Hofstra Northwell School of Medicine, New York, NY, USA.
authors.forename: Seyed Behzad
authors.initials: SB
authors.lastname: Jazayeri
authors.affiliation: Department of Urology, Lenox Hill Hospital, Hofstra Northwell School of Medicine, New York, NY, USA.
authors.forename: David B
authors.initials: DB
authors.lastname: Samadi
keywords: AS, active surveillance; ASA, American Society of Anesthesiologists; Active surveillance; BMI, body mass index; Gleason; MRI; Prostate cancer; RALP, robot-assisted laparoscopic prostatectomy; Tumour size