[826] The Utility of Novel Immunohistochemical Marker ERG in Detecting Prostate Cancer Following Atypical Prostate Biopsies: Will New Tumor Markers Be of Value in Such Circumstance?

Huiying He, Cristina Magi-Galluzzi, Paula Carver, Sara Falzarano, Karen Smith, Mark Rubin, Ming Zhou. Cleveland Clinic; Weill Cornell Medical College, New York; Peking University, Health Science Center, Beijing, China

Background: A diagnosis of 'Atypical glands suspicious for cancer' (ATYP) in prostate biopsy (PBx) is associated with an average of 42% risk of detecting prostate carcinoma (PCa) in subsequent PBx. Many studies have failed to identify any clinical, histological or molecular characteristics of ATYP that could predict which patients would have PCa in the follow-up. TMPRSS2: ERG gene rearrangement is highly specific and is present in approximately 50% of PCa. Recently, a novel anti-ERG monoclonal antibody, when used as an immunohistochemical (IHC) marker, has been found to highly correlate with TMPRSS2: ERG gene rearrangement status. We evaluated the utility of this antibody on PBx with initial ATYP diagnosis to determine whether ERG expression could help improve PCa detection in subsequent PBx.
Design: ERG protein expression was evaluated by IHC on 103 cases of PBx with initial ATYP diagnosis. The pathological features of ATYP and ERG expression were correlated to the PCa detection in follow-up PBx.
Results: ERG expression was detected in 16/103 (15.5%) PBx with an initial ATYP diagnosis. Of the 16 ERG positive cases, the atypical glands were positive for ERG in 9 cases. In remaining 7 cases, positive ERG staining was found in the glands other than ATYP glands, including low and high grade prostatic intraepithelial neoplasia, and morphologically benign glands. In 49 cases with confirmed PCa diagnosis, 7 (14.2%) was positive for ERG in ATYP biopsy. PCa was detected in 7/16 (43.8%) of ERG-positive cases, and in 42/87 (48.3%) of ERG-negative cases in subsequent PBx (p=0.841 by x2 test). ATYP was categorized as “favor cancer”, “indeterminate” and “favor benign”. PCa was detected in 18/29 (62.1%), 24/42 (57.1%) and 7/32 (21.9%) (p=0.002 by x2 test) in the 3 categories. Addition of ERG IHC results did not improve the cancer detection in the 3 categories.
Conclusions: ERG-positive glands were present in 15.5% of ATYP PBx. However, the positive ERG stain did not correlate with increased cancer detection in subsequent PBx. The most likely explanation is that while positive ERG IHC identifies patients who harbor PCa, PCa in these patients is under-detected by the current PBx protocols. Our results suggest that new PCa markers have limited contribution to the ultimate PCa detection as long as the diagnosis of PCa depends on the detection of cancer tissue by PBx which currently has significant false negative rate.
Category: Genitourinary (including renal tumors)

Monday, February 28, 2011 8:15 AM

Platform Session: Section A, Monday Morning


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