The performance of targeted magnetic resonance imaging/ultrasound fusion biopsy versus random 12-core biopsy for prediction of total prostate cancer tumor volume.

Abstract

34 Background: Tumor quantification with percent core and/or core length involvement is a parameter used to determine burden of disease for patients with prostate cancer (PCa). However, controversy exists regarding tumor quantification in random 12-core biopsies due to discrepancies in lesion targeting and overall needle core lengths obtained. Targeted MRI/US fusion biopsy allows for more optimal lesion targeting and interpretation of this parameter. We aim to correlate highest percentage core involvement and corresponding tumor length for both targeted fusion and random 12-core biopsies with total tumor volume. Methods: Patients who underwent multiparametric MRI (MP-MRI) with targeted MRI/US fusion biopsy at our institution between 2007 and 2012 were reviewed. Those that met Johns Hopkins criteria for active surveillance (AS) based on outside 12−core biopsy were then identified. MRI tumor volumes were calculated in fusion biopsy positive lesions and correlated with the highest percentage core involvement and corresponding tumor length for both targeted fusion biopsy and 12-core biopsy. Bivariate analysis was used to determine the empirical relationship between these variables. Results: Six hundred ninety six patients had MP-MRI with MRI/US fusion biopsy, 109 of which met Johns Hopkins criteria for AS upon entry and 47 of these patients had fusion biopsy confirmed PCa. Mean age was 61 and mean PSA was 5.6ng/ml. For highest percentage core involvement, targeted biopsy showed a positive correlation (r=0.57) whereas 12-core biopsy showed a poor correlation (r=0.016) with the total tumor volume (p<0.0001 and p=0.91 respectively). Similarly, for tumor length of the highest percentage core, targeted biopsy showed a positive correlation (r=0.6) whereas 12-core biopsy showed a poor correlation (r=0.01) with the total tumor volume (p<0.0001 and p=0.94 respectively). Conclusions: Highest percentage core involvement and corresponding tumor length on targeted MRI/US fusion biopsy positively correlate with total tumor volume. Targeted biopsy better predicts overall burden of disease and can aid in risk stratification of patients seeking AS.