[869] ERG Immunoexpression Does Not Predict Risk of Recurrence after Prostatectomy for Clinically-Localized Prostate Cancer

Nilda D Gonzalez-Roibon, Sarah Peskoe, Alcides Chaux, Roula Albadine, Jessica Hicks, Angelo De Marzo, Elizabeth A Platz, George J Netto. The Johns Hopkins University SOM, Baltimore, MD; The Johns Hopkins Bloomberg School of Public Health, Baltimore, MD

Background: We previously demonstrated that TMPRSS2-ERG fusion detected by FISH does not predict recurrence of localized prostate cancer after prostatectomy. We also demonstrated that ERG immunoexpression is a suitable surrogate for ERG fusion. Herein we evaluate the role of ERG protein immunoexpression as a predictor of recurrence in clinically-localized prostate cancer, independent of known clinicopathological factors.
Design: A nested case-control study was conducted in patients who underwent radical prostatectomy for clinically-localized prostate cancer at our institution between 1993 and 2004. The study included tumors from 444 cases (recurrence) and 444 controls (nonrecurrence). Patients were matched for age, race, Gleason sum, and pathologic stage. Cases were defined by the presence of biochemical recurrence, metastasis, or prostate cancer death. Triplicate tissue cores were used to construct the 16 tissue microarrays (TMAs) set. ERG protein nuclear expression was evaluated using immunohistochemistry as previously described (Am J Surg Pathol 2011; 35:1014). In each tumor spot, an H-score was calculated as the sum of the product of nuclear staining intensity (0 to 3+) and the extent (percentage). ERG expression for each patient was classified based on 1) the patient having any positive TMA spot, and 2) the mean H score across a patient's TMA spots. The odds ratio (OR) of recurrence was estimated using conditional logistic regression to take into account the matching factors and to adjust for year of surgery, preoperative serum PSA level, and status of surgical margins.
Results: After multivariable adjustment, 48.5% of the recurrence cases and 48.3% of the nonrecurrence controls had ERG expression in any TMA spot (P = 0.97). Further, no association was found between ERG positivity (OR 0.87; 95% CI 0.60, 1.25; P = 0.45) or the extent of ERG staining (versus no staining; 0 < H score < 165: OR 0.70, 95% CI 0.44, 1.12; H score ≥ 165: OR 1.04, 95% CI 0.67, 1.62) and risk of recurrence.
Conclusions: Prostate tumor immunohistochemical expression of ERG protein did not predict recurrence in patients treated by radical prostatectomy for clinically-localized disease.
Category: Genitourinary (including renal tumors)

Monday, March 19, 2012 1:00 PM

Poster Session II # 162, Monday Afternoon

 

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