Introduction

mpMRI offers the possibility to locate cancer in 3-Dimensions and aid surgical planning. We investigated the margin needed around an mpMRI lesion for complete disease control in a prospectively enrolled biopsy naïve population who underwent mpMRI followed by Transperineal Prostate Mapping with biopsies taken every 5mm(5TPM)._x000D_ _x000D_

Methods

94 patients included in this analysis were part of the pilot phase of Prostate MRI Imaging Study (NCT01292291) investigating accuracy of mpMRI against standard of care with TPM as a reference test. All patients were biopsy-naïve with a PSA below 15ng/ml. All patients underwent 1.5T mpMRI with standardized protocol (T2W, Diffusion, DCE), blinded reported using Likert scoring. Each core was separately labelled and oriented in space. Each prostate and MRI lesion was contoured on T2W-imaging, blinded to pathology. A 3D digital map of the TPM was reconstructed using an in-house software. Correlation between mpMRI and biopsy findings was automatically carried out using a platform generating the registration based on landmarks. We report the margin ‘M’ around the MRI lesion as the maximum distance within a set of negative biopsy location surrounding the MRI lesion. Results are also stratified by MRI score, Gleason Score, lesion eligibility to focal therapy and significance.

Results

41 patients (median PSA 6.5ng/ml, median age 62) were found to harbour cancer at 5TPM in this cohort, yielding 75 MRI lesions that corresponded to cancer at 5TPM. The median number of MRI lesions per patient was 1.5. As a control of registration, correlation between MRI volume and TPM volume was ?=0.92 (p<0.001). Lesion characteristics are summarized in Table 1. The mean margin (enclosing a perimeter of negative cores) for MRI lesions corresponding the cancer at 5TPM was 7.0 mm (SD 4.6mm). For lesion eligible for focal therapy (n= 35), the mean margin was 7.3 (SD 4.3mm). The mean Gleason score of biopsy core outside the MRI lesion was 6.7 (+/- 0.5)._x000D_ _x000D_ _x000D_

Conclusions

Our study is the first to report a margin around a mpMRI lesion when based on prostates that have not been removed using surgery and evaluated against a very accurate 3-dimensional 5mm mapping biopsy. These findings have implications for focal therapy and nerve-sparing surgery._x000D_ _x000D_

Funding

Medical Research Council UK