PURPOSE: To compare boundaries of prostate tumors on MRI and histologic assessment from radical prostatectomy (RP) using detailed software-assisted co-registration, in order to define an optimal treatment margin to achieve complete tumor destruction during image-guided focal ablation.
METHODS: 33 patients who underwent 3T MRI before RP were included. A radiologist traced lesion borders on MRI and assigned a suspicion score (SS) from 2-5. 3D reconstructions were created from high-resolution digitalized slides from RP specimens and co-registered to MRI using advanced software. Tumors were compared between histology and MRI using the Hausdorff Distance (HD) and stratified by MRI-SS, Gleason Score (GS), and lesion diameter. Cylindrical volume estimates of treatment effects were used to define the optimal treatment margin.
RESULTS: 46 histologically confirmed cancers underwent 3D software-based registration with MRI. MRI underestimated tumor sizes, with the maximal discrepancy between MRI and histologic boundaries for a given tumor averaging 1.99±3.1mm (18.5% of the MRI diameter). Boundary underestimation was larger for MRI-SS≥4 lesions (+3.49±2.1mm; p< 0.001) and GS≥7 lesions (+2.48±2.8mm; p 0.035). On average, a simulated cylindrical treatment volume based on the MRI boundary missed 14.8% of the tumor volume compared with a simulated cylindrical volume based on the histologic boundary. A simulated treatment volume based on a 9mm treatment margin achieved complete histologic tumor destruction in 100% of patients.
CONCLUSION: MRI underestimates histologically-determined tumor boundaries, especially for high MRI-SS and high GS lesions. A 9mm treatment margin around an MRI-visible lesion consistently ensures treatment of the entire histologic tumor volume during focal ablative therapy.
Le Nobin J, Rosenkrantz AB, Villers A, Orczyk C, Deng FM, Melamed J, Mikheev A, Rusinek H, Taneja SS. Are you the author?
Division of Urologic Oncology, Department of Urology, New York University Langone Medical Center, New York, NY, USA; Department of Urology, University Hospital of Lille, Lille, France; Department of Radiology, New York University Langone Medical Center, New York, NY, USA; Department of Urology, University Hospital of Lille, Lille, France; Department of Urology/ UMR 6301-Cervoxy Group, University Hospital of Caen, France; Department of Pathology, New York University Langone Medical Center, New York, NY, USA.
Reference: J Urol. 2015 Feb 21. pii: S0022-5347(15)00389-4.