Abstract 2580: A mosaic ERG oncoprotein staining pattern predicts upstaging and poor pathologic features in prostate cancer patients

Abstract

Abstract Purpose: Building on previous work, this study examined the independent role of ERG staining pattern in the index prostate cancer (CaP) tumor, on probability of upstaging and biochemical recurrence (BCR) following radical prostatectomy (RP). Methods: A retrospective cohort study of patients enrolled at the Walter Reed National Military Medical Center who underwent RP between 1993 and 2016 was conducted. ERG oncoprotein expression was assessed in CaP index tumors (i.e., largest and poorest grade) using immunohistochemistry (IHC) staining with 9FY monoclonal antibody of representative sections of formalin-fixed paraffin-embedded whole-mounted RP specimens. ERG status was classified as positive (ERG+), negative (ERG-) and a pattern of alternating +/- regions within the index tumor (ERG “Hybrid” or ERG-h). Kaplan Meier (KM) estimation curve analysis was used to examine BCR-free survival across ERG status. Multivariable (MV) logistic regression (LR) modeling was used to determine whether ERG status predicted upstaging (cT1-2 to pT3-4). Results: Among 1,385 eligible patients, mean age at RP and follow up time were 58.8 and 7 years, respectively. Twenty-nine percent of patients self-classified as African-American (AA), and 18% experienced BCR. The ERG-h pattern was observed in 81 patients (5.8%). Pathologic stage T3a-T4a was observed in 51.3%, 32.2% and 30.5% of patients with ERG-h, ERG+ and ERG- tumors, respectively. In unadjusted KM analysis, 10-year BCR-free survival probabilities were 78%, 75%, and 82% for ERG-h, ERG-, and ERG+ patients, respectively (p=0.08). A trend of incrementally poorer BCR-free survival was observed for ERG-h, ERG- versus ERG positive patients. MV LR analysis revealed the greatest odds of upstaging for ERG-h vs. ERG- patients (OR=2.8, p=0.0008), controlling for age at RP (p<.0001), biopsy Gleason score (p<.0001), PSA at diagnosis (p=0.0054) and patient race (p=0.07). Conclusions: In this racially diverse cohort of RP patients, a mosaic-like pattern of ERG staining predicted greater upstaging and poorer pathologic features. There may be a role for examination of this “hybrid” mosaic staining pattern in patient risk stratification during treatment decision making. Citation Format: William Gesztes, Shahnoza Dusmatova, Justin Mygatt, Jennifer Cullen, Denise Yong, Huai-Ching Kuo, Yongmei Chen, Lauren Hurwitz, Inger Rosner, Shiv Srivastava, Isabell Sesterhenn. A mosaic ERG oncoprotein staining pattern predicts upstaging and poor pathologic features in prostate cancer patients [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 2580.