Introduction

Accurate prostate cancer risk stratification is essential to guide decision making on active surveillance and interventional therapy. The aim of this study was to determine if a targeted biopsy strategy to sample only MRI detected lesions could replace standard practice of systematic prostate biopsies.

Methods

Prostate MRI scans of all patients undergoing RARP for prostate cancer between 2013 and 2016 were prospectively analysed with a uro-radiologist as part of an established quality assurance program. MRI scans were graded as optimal or suboptimal by the radiologist. Localisation of MRI detected prostate cancer (represented in a diagram) was compared to histopathological mapping of cancer following RALP. Significant out of MRI field cancer was defined as Gleason ≥3+4. Location was analysed according to 5 different zones: Anterior, left posterolateral, right posterolateral, apex and base.

Results

The median Age, PSA and Gleason score were 62.9 (4576), 10.67 (156) and 7 (610) respectively. 778 (89.7%) of patients had ? pT2c. Significant prostate cancer was found in 2418/4335 zones (55.8%) on final postoperative pathology. MRI was able to pick up 1797/2418 (74.3%) of the significant lesions and missed 25.7%. Of these significant lesions, 34.7% were ≥4+3. Optimal MRI scans picked up more significant lesions than suboptimal scans (79.6% vs 71.4%). The overall sensitivity of MRI to detect significant prostate cancer was 71.2%, specificity 84.9%, PPV 85.6% and NPV 63.4%. Cohen's Kappa coefficient varied from 0.12 (poor) to 0.44 (moderate)? Area under the ROC curve ranged from 0.572 to 0.722 with apical and anterior lesions having lower values. Individual zonal accuracy data is as per table 1.

Conclusions

Our results show that in a population of men with significant prostate cancer, MRI can reliably detect significant prostate cancer in in 85.6% of the time. A targeted strategy using MRI will have a 36.6% chance of non detection of significant invisible cancer.

Funding

None