Ability of multiparametric magnetic resonance imaging (MRI) to predict prostate tumor heterogeneity on targeted biopsy.

Abstract

113 Background: Prostate cancer (PCa) can show heterogeneous histology within lesions. MRI-targeted biopsy (Tbx) of the prostate improves PCa detection, but sampling within lesions has yet to be standardized. Furthermore, Tbx results are often heterogeneous as evidenced by differing histologic grades of Tbx cores within the same lesion. This introduces potential variability in biopsy results, on which clinical decisions are made. Here we aim to characterize lesion heterogeneity and identify predictive multiparametric MRI (mpMRI) features. Methods: A cohort of men who underwent mpMRI and Tbx between 2014-2017 were selected for analysis from a prospectively maintained database. To characterize lesion heterogeneity, only men with ≥2 positive Tbx cores were included. Histologic grades were scored according to International Society of Urological Pathology (ISUP) grades. Lesion heterogeneity, reported as a heterogeneity index (HI), was calculated as the difference of the average ISUP grades of Tbx cores per lesion from the maximum sampled ISUP grade of that lesion. Statistical analyses identified associations between imaging features and lesion heterogeneity. Results: 157 lesions in 114 patients met inclusion criteria. Maximum ISUP grade ranged from 1 to 5, with a median ISUP grade of 2. Higher ISUP grades were associated with greater lesion heterogeneity, HI for ISUP grade ≥3 = 0.58±0.11 vs <3 = 0.29±0.08, p = 0.0001. In addition, increasing lesion size on mpMRI was associated with greater lesion heterogeneity, HI for ≥2cm = 0.52±0.14 vs <2cm = 0.32±0.08, p = 0.0096. Finally, higher mpMRI suspicion scores were associated with increased heterogeneity vs lower suspicion scores, p = 0.048. Conclusions: mpMRI aids in characterizing PCa lesion heterogeneity to predict variability of histologic grades on Tbx. This information can assist Tbx planning to potentially reduce risks of upgrading on final pathology. Future research will examine how lesion heterogeneity can impact risk stratification and clinical decision-making for patients and practitioners. This research was supported by the Intramural Research Program of the National Cancer Institute, NIH and NIH Medical Research Scholars Program.