PTEN and ERG Detection in Multiparametric Magnetic Resonance Imaging/ultrasound Fusion Targeted Prostate Biopsy Compared to Systematic Biopsy

Multiparametric magnetic resonance imaging (MRI)/ultrasound fusion targeted prostate biopsy has been shown to outperform systematic biopsy in the detection of clinically significant prostate cancer. Aside from tumor grade, tumor biomarkers such as phosphatase and tensin homolog (PTEN) and ETS-related gene (ERG) have prognostic significance in prostate cancer and may help direct management of patients with low-grade tumors. Our objective was to compare the detection of PTEN and ERG expression in MRI-targeted versus systematic prostate biopsies. We compared immunohistochemical expression for PTEN and ERG on prostate biopsy cores from patients with Grade Group (GG) 1 or GG2 prostate cancer who had undergone systematic biopsy with concurrent targeted biopsy. Fifty-three cases had both systematic and MRI-targeted prostate tissue available for staining for PTEN; and 52 cases, for ERG. ERG positivity was seen in 37/52 (71.2%) cases, and PTEN loss was seen in 15/53 (28.3%) cases. The detection of ERG expression was not significantly different between MRI-targeted and systematic biopsy (P = .4). Targeted biopsy was superior to systematic biopsy in the detection of PTEN loss (P = .02). MRI-targeted cores detected 14/15 (93.3%) cases of PTEN loss compared to 7/15 (46.7%) cases detected by systematic cores. Most cases with PTEN loss showed heterogeneous expression in both systematic and targeted cores. In 14/15 (93.3%) cases with PTEN loss, GG was the same between targeted and systematic biopsy. Targeted biopsy is superior to systematic biopsy in the detection of PTEN loss in GG1 and GG2 tumors. Inclusion of targeted cores may be helpful for evaluation of certain prognostic biomarkers.