C-choline PET is superior to T2-weighted MRI for localising malignant intraprostatic lesions for guiding prostate cancer focal therapies.

Abstract

BACKGROUND: To compare the accuracy of 11C-choline (CHOL) positron emission tomography (PET) with T2-weighted (T2W) magnetic resonance imaging (MRI) for delineating malignant intraprostatic lesions (IPLs) for focal therapies and to investigate factors predicting the accuracy of CHOL PET. METHODS: This prospective study included thirty patients who underwent CHOL PET and MRI prior to radical prostatectomy. Two observers manually delineated IPL contours for each scan, and automatic IPL contours were generated on CHOL PET based on varying proportions of the maximum standardised uptake value (SUV). IPLs identified on prostatectomy specimens defined the reference standard contours. The imaging-based contours were compared with the reference standard contours using Dice similarity coefficient (DSC), sensitivity and specificity. Factors that could potentially predict the DSC of the best contouring method were analysed using linear models. RESULTS: The best automatic contouring method, SUV60, had significantly better correlations (DSC 0.602) than the manual PET contours (DSC 0.517, P = 0.027) and the manual MRI contours (DSC 0.310, P < 0.001). The sensitivity and specificity values were 75.0% and 69.7% for SUV60; 52.0% and 86.2% for PET manual contouring; and 23.8% and 95.4% for MRI manual contouring. The tumour volume and transition zone pattern could independently predict the accuracy of CHOL PET. CONCLUSIONS: CHOL PET is superior to T2W MRI; and SUV60 automatic contouring is superior to manual contouring for delineating IPLs for focal therapies. The transition zone pattern is a new classification that may predict for how well CHOL PET delineates IPLs.