What Burden of Prostate Cancer Can Radiologists Rule Out on Multiparametric Magnetic Resonance Imaging? A Sensitivity Analysis Based on Varying the Target Condition in Template Prostate Mapping Biopsies.

OBJECTIVE - To evaluate the minimum disease burden of prostate cancer at which multiparametric magnetic resonance imaging (MRI) optimally performs.

METHODS - Between 2006 and 2008, 64 men underwent multiparametric MRI imaging (index test) followed by template prostate mapping biopsy (reference test). Three radiologists independently reported each quadrant of every prostate on a scale of 1 to 5: highly likely benign, likely benign, equivocal, likely malignant, highly likely malignant (≥3 or ≥4 was considered positive). There were 256 prostate sectors; bootstrapping adjustment was used to account for nonindependence. The target condition indicating cancer on biopsies was varied by changing the maximum cancer core length (MCCL) and total cancer core length (TCCL) within each sector from 1 mm to 10 mm. The sensitivity, specificity, and positive (PPVs) and negative predictive values (PPVs) were calculated for each MCCL and TCCL. Gleason ≤3+3 and Gleason ≥3+4 cancers were analyzed separately.

RESULTS - Mean age was 62 years (range, 40-76 years), and mean prostate-specific antigen level was 8.2 μg/L (range, 2.1-43 μg/L). Fifty percent of quadrants (127 of 256) had prostate cancer, of which 65% (83 of 127) were Gleason ≤3+3. For Gleason ≤3+3, multiparametric MRI had an NPV of ≥95% at an MCCL of ≥5 mm and at a TCCL of ≥7 mm (MRI score ≥3). For Gleason ≥3+4, an NPV of ≥95% was seen at an MCCL of ≥5 mm (MRI score ≥3) and TCCL ≥6 mm.

CONCLUSIONS - Multiparametric MRI may allow areas of the prostate which test negative to avoid biopsy. Whether multiparametric MRI can be used as a "triage" test before the first biopsy requires results from ongoing prospective validating cohort studies.

Urology. 2015 Aug 4. pii: S0090-4295(15)00479-3. doi: 10.1016/j.urology.2015.05.010. [Epub ahead of print]

Anastasiadis E1, Charman SC2, Arumainayagam N3, Sohaib AS4, Allen C5, Freeman A6, Emberton M7, Ahmed HU7.

1 Clinical Effectiveness Unit, Royal College of Surgeons of England, London, United Kingdom.
2 Department of Health Services Research and Policy, London School of Hygiene and Tropical Medicine, London, United Kingdom.
3 Division of Surgery and Interventional Science, University College London, London, United Kingdom.
4 Department of Radiology, The Royal Marsden Hospital, London, United Kingdom.
5 Department of Imaging, University College London Hospitals NHS Foundation Trust, London, United Kingdom.
6 Department of Histopathology, University College London Hospitals NHS Foundation Trust, London, United Kingdom.
7 Division of Surgery and Interventional Science, University College London, London, United Kingdom; Department of Urology, University College London Hospitals NHS Foundation Trust, London, United Kingdom.

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