title: Role of MRI in low-risk prostate cancer: finding the wolf in sheep's clothing or the sheep in wolf's clothing?
abstract: OBJECTIVE
  In men on active surveillance for localized prostate cancer, MRI and MRI-targeted biopsies can be used prior to confirmatory or surveillance biopsy, to detect individuals with high-grade cancer (the wolf in sheep's clothing). However, some men will have low-risk disease despite adverse MRI findings (the sheep in wolf's clothing). We review the value addition of MRI-targeted biopsies in comparison to systematic transrectal ultrasound-guided biopsies, using pathological reclassification as an end-point.
  
  
  RESULTS
  At confirmatory and surveillance biopsies, both the MRI-targeted and repeat standard biopsies have shown value in identifying histologically adverse findings in men with low-risk prostate cancer. For maximal detection of clinically significant cancer, a prebiopsy MRI should be performed together with both MRI-targeted and systematic transrectal ultrasound-guided biopsies. Stable disease on MRI may reduce the need for serial biopsies in some men on active surveillance.
  
  
  CONCLUSIONS
  Prostate MRI and subsequent MRI-targeted biopsies are worthwhile to the current management of men with low-risk prostate cancer on active surveillance. Prostate MRI, in combination with a multivariable risk-prediction model may help in identifying both the wolf in sheep's clothing and the sheep in wolf's clothing, and in potentially reducing the need for serial biopsies.
authors.affiliation: aDepartment of Radiology & Nuclear Medicine, Erasmus MC University Medical Center, Rotterdam bDepartment of Radiology, The Netherlands Cancer Institute, Amsterdam, The Netherlands cDivision of Surgical and Interventional Science, University College London dDepartment of Urology, University College London Hospitals Trust, London, United Kingdom eHospices Civils de Lyon, Department of Urinary and Vascular Imaging, Hôpital Edouard Herriot fUniversité de Lyon, faculté de médecine Lyon Est, Lyon, France.
authors.forename: Ivo G
authors.initials: IG
authors.lastname: Schoots
authors.forename: Caroline M
authors.initials: CM
authors.lastname: Moore
authors.forename: Olivier
authors.initials: O
authors.lastname: Rouvière
mesh_terms: D006801:Humans; D061705:Image-Guided Biopsy / Q000379:methods*; D008279:Magnetic Resonance Imaging; D008297:Male; D011467:Prostate / Q000000981:diagnostic imaging*; D011471:Prostatic Neoplasms / Q000000981:diagnostic imaging*