[1028] Significance of Increased Frequency of Her2/Neu Expression in Intraductal Carcinoma of the Prostate in Comparison to Conventional Prostatic Adenocarcinoma

Thomas M Schneider, Adeboye O Osunkoya. Emory University School of Medicine, Atlanta, GA

Background: Intraductal carcinoma of the prostate (IDC-P) is an aggressive variant of prostatic adenocarcinoma. HER2/neu is a protein that is expressed by the ERBB2 gene. The over expression of the ERBB2 gene is common in a number of malignancies, especially breast cancer, and HER2/neu is the target of monoclonal antibody Trastuzumab (Herceptin). Low levels of HER2/neu expression have recently been described in 17-20% of cases of conventional prostatic adenocarcinoma, with a greater incidence in cases with higher Gleason scores. In this study, we examined the expression of HER2/neu in IDC-P.
Design: Confirmed cases of IDC-P were identified at our institution from the surgical pathology files and consultation cases of the senior author. Immunohistochemical stains were performed for HER2/neu using a rabbit anti-HER2 monoclonal antibody. The HER2/neu expression in the IDC-P component was documented. Per protocol, staining intensity of HER2/neu was interpreted as 0, 1+, 2+ or 3+.
Results: Thirty one cases of IDC-P were identified. HER2/neu expression was as follows: 0 staining was identified in 11/31 (35%) cases, 1+ staining was identified in 12/31 (39%) cases, 2+ staining was identified in 6/31 (19%) cases, and 3+ staining was identified in 2/31 (7%) cases. Therefore, 20/31 (65%) cases had variable degrees of expression of HER2/neu, which is higher than is documented in the literature for conventional prostatic adenocarcinoma.
Conclusions: Although low levels of Her2/neu expression is known to occur in 17-20 % of conventional prostatic adenocarcinoma, this study is the first to date to evaluate HER2/neu expression in IDC-P, and demonstrates that Her2/neu expression (low levels or overexpression) occurs in over 60% of patients with IDC-P. The increase in frequency of HER2/neu expression in this aggressive subset of prostatic adenocarcinoma indicates that patients with IDC-P may benefit from clinical trials with Trastuzumab (Herceptin) or newer generations of more efficient anti-Her2 drugs, such as the anti-Her2 recombinant humanized monoclonal antibody, possibly with modified protocols.
Category: Genitourinary (including renal tumors)

Wednesday, March 6, 2013 9:30 AM

Poster Session V # 119, Wednesday Morning


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