[834] ERG-Immunopositivity in Prostatic Adenocarcinoma Is Unrelated to Aggressive Local Tumor Characteristics or to Biochemical Recurrence: A Study of 454 Cases

Myriam Chevarie-Davis, Simone Chevalier, Eleonora Scarlata, Alice Dragomir, Simon Tanguay, Wassim Kassouf, Armen Aprikian, Fadi Brimo. McGill University, Montreal, QC, Canada

Background: ERG mutations are among the most frequent genetic anomalies in prostate adenocarcinomas (PCa). While positive immunostaining for ERG was shown to highly correlate with ERG fusion status, the clinical and prognostic significance of a positive ERG stain in PCa remains undetermined. Numerous related studies have yielded contradictory results with some showing a clear association with adverse prognosis, others showing a favourable association, and some being unable to demonstrate any relation between ERG and clinico-pathological parameters. We herein evaluate the significance of ERG immunostaining in a large cohort of PCa from radical prostatectomies (RP) with long term follow-up, and we also compare ERG status in peripheral zone PCa vs transitional zone PCa.
Design: Eight tissue microarrays (TMA) including duplicate cores of 454 consecutive PCa (from RPs) from our institution were evaluated using ERG immunostain and constituted the main study set. A separate set of 59 cases of incidental PCa detected on trans-urethral resection of prostate (TURP) with Gleason score (GS) of 6 was also included. Staining intensity was graded using a four-tiered system (0-1-2-3). ERG status and staining intensity were correlated with various clinical and pathological parameters including biochemical recurrence (BCR).
Results: Pathologic (T)-stage of the main cohort was T2, T2+, T3A and T3B in 59%, 13%, 23% and 5%, respectively. The final GS was 6, 7 and 8-10 in 29%, 63% and 8%, respectively. Of the 307 patients with available clinical follow-up (mean follow-up of 5.5 years), 27% recurred after a mean time of 2.8 years post-RP. ERG positivity was detected in 33% of TMA cases. In these cases, although ERG-positivity was significantly associated with younger age at presentation (p = 0.0018) and lower PSA values (p=0.03), it showed no association with final GS nor pathologic stage. On multivariate analysis, BCR was only associated with final GS (p=0.001) and elevated PSA levels (p=0.04) and was unrelated to either ERG-positivity or its staining intensity. In comparison, ERG positivity in incidental PCa detected on TURP was only 5%.
Conclusions: ERG mutations are much more common in peripheral zone PCa in comparison to those of transitional zone. In our hands, ERG positivity was unrelated either to aggressive local tumor characteristics or to a worse outcome.
Category: Genitourinary (including renal tumors)

Tuesday, March 5, 2013 11:30 AM

Proffered Papers: Section A, Tuesday Morning


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