ASCO GU 2018: Ability of multiparametric MRI to predict prostate tumor heterogeneity on targeted biopsy

San Francisco, CA ( Dr. Samuel Gold presented their teams research assessing the ability of multiparametric MRI (mpMRI) to predict prostate tumor heterogeneity on targeted biopsy. Indeed, prostate cancer can show heterogeneous histology within lesions. Although MRI-targeted biopsy of the prostate improves prostate cancer detection, sampling within lesions has yet to be standardized. Additionally, targeted biopsy results are often heterogeneous as evidenced by differing histologic grades of targeted biopsy cores within the same mpMRI lesion, introducing variability in biopsy results. The objective of this study was to characterize lesion heterogeneity and identify predictive mpMRI features.

The authors identified 157 lesions among 114 patients that met inclusion criteria from 2014-2017 who underwent mpMRI and targeted biopsy. To characterize lesion heterogeneity, only men with ≥2 positive targeted biopsy cores were included in the study. Histologic grades were scored according to International Society of Urological Pathology (ISUP) grades. Lesion heterogeneity was reported as a heterogeneity index (HI) and calculated as the difference of the average ISUP grades of targeted biopsy cores per lesion from the maximum sampled ISUP grade of that lesion. 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). Second, 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 (0.46 ± 0.48 vs 0.31 ± 0.35; p = 0.033).

The authors concluded that mpMRI aids in characterizing prostate cancer lesion heterogeneity to predict variability of histologic grades on targeted. This information may assist targeted planning to potentially reduce risks of upgrading on final pathology. The authors noted that future research will examine how lesion heterogeneity can impact risk stratification and clinical decision-making for patients and practitioners. 

Presented by: Samuel Gold, National Cancer Institute, Bethesda, MD

Co-Authors: Jonathan Bloom, Graham R. Hale, Kareem Rayn, Sherif Mehralivand, Brad J. Wood, Baris Turkbey, Peter A. Pinto

Written By: Zachary Klaassen, MD, Urologic Oncology Fellow, University of Toronto, Princess Margaret Cancer Centre at the 2018 American Society of Clinical Oncology Genitourinary (ASCO GU) Cancers Symposium, February 8-10, 2018 - San Francisco, CA