[885] Frequency of ERG Rearrangement in a Swedish Hospital Based Biopsy Cohort

MA Svensson, S Perner, F Demichelis, G Helenius, PW Kantoff, SO Andersson, O Andren, MA Rubin. Weill Cornell Medical College, New York, NY; Orebro University Hospital, Orebro, Sweden; Harvard Medical School, Boston, MA; Dana-Farber Cancer Institute, Boston, MA

Background: Recurrent gene fusions between TMPRSS2 and ETS transcription factor family members, most often ERG, are seen in 40-80% of prostate cancers (PCa). The frequency of TMPRSS2-ERG fusion in two recent Watchful Waiting cohorts, where tumor samples were obtained from incidental transurethral resection of the prostate (TURP) samples demonstrated TMPRSS2-ERG fusion frequency of 15% and 17.5%. The aim of this study was to investigate if this significant difference in ETS rearrangement frequency was particular to the Swedish population or incidental PCa.
Design: We assessed the ERG rearrangement by fluorescence in-situ hybridization (FISH) using an ERG break-apart assay on a needle biopsy based PCa cohort from Sweden. This Swedish population based biopsy cohort consists of 96 men consecutively diagnosed with localized or advanced (T1-T3, Nx, M0-M1) PCa between 1989 and 1990 at the Department of Urology, Orebro University Hospital in Sweden.
Results: We observed that 74% (71/96) of the cases could be assessed for ERG rearrangement. Of these cases 45% (32/71) demonstrated ERG rearrangement, with 62.5% (20/32) being rearranged with deletion and 37.5% (12/32) being rearranged with insertion. We detected an increase in percentage of ERG rearranged cases with increasing tumor stage (T1 23.1%, T2 45.5% and T3 52.8%). Gleason score and nuclear grade were not associated with ERG rearrangement.
Conclusions: The 45% ERG fusion PCa observed in this cohort is comparable to the frequency of other hospital-based cohorts in other countries including a recent prospective study conducted by the Early Research Detection Network (EDRN). This indicates that the fusion frequency of 15% and 17.5% in the incidental Swedish Watchful Waiting cohorts may be due to lower tumor stage or tumor location and not due to ethnic differences.
Category: Genitourinary (including renal tumors)

Monday, March 9, 2009 1:00 PM

Poster Session II # 109, Monday Afternoon