[857] The Relationship of TMPRSS2-ERG Gene Fusion between Primary and Metastatic Prostate Cancers

CC Guo, Y Wang, L Xiao, I Prokhorova, P Troncoso, BA Czerniak. University of Texas MD Anderson Cancer Center, Houston, TX

Background: Most prostate cancers carry a chromosomal rearrangement leading to the fusion of TMPRSS2 and ERG genes. The TMPRSS2-ERG gene fusion has been found in both primary and metastatic prostatic cancers. However, the relationship of the TMPRSS2-ERG gene fusion between primary and metastatic prostate cancers remains unclear.
Design: We selected 23 radical prostatectomy specimens (RPS) and corresponding lymph node metastases. Histologic slides were reviewed for pathologic analysis. TMPRSS2-ERG gene fusions in all primary tumor foci of the RPS and metastases were evaluated by fluorescence in situ hybridization (FISH) using ERG break-apart probes.
Results: The average age of the patients was 64.4 years (range, 44-82 years). In the RPS, the median Gleason score of the tumor was 7 (4+3) (range, 7-9); the tumors were unifocal in 10 cases and multifocal in 13 cases, including 2 foci (n=10) and 3 foci (n=3). In the multifocal prostate cancers, the index or largest tumor foci had a mean volume of 3.8 cm3, while the secondary tumor foci had a mean volume of 0.3 cm3 with a median Gleason score of 6 (3+3). In the RPS, rearrangement of the ERG gene was present in 15 cases and the arrangement was associated with deletion of the 5' ERG gene in 9 cases. In the metastases, rearrangement of the ERG gene was present in 12 cases and the rearrangement was associated with a deletion of the 5' ERG gene in 7 cases. In unifocal prostate cancers, rearrangement of the ERG gene was present in 7 cases, and there was concordance of the ERG gene rearrangement status between the primary tumor and the metastasis in 9 of 10 cases. In multifocal prostate cancers, rearrangement of the ERG gene was present in 8 cases, including in the index tumor focus only (n=4), a secondary tumor focus only (n=2), or both (n=2). All 13 cases of multifocal prostate cancers showed concordance of the ERG gene rearrangement status between the metastasis and the primary index tumor focus.
Conclusions: Our study demonstrates concordance of TMPRSS2-ERG gene fusion status between primary and metastatic prostate cancers in the majority of unifocal prostate cancers. Although there is discordance of TMPRSS2-ERG gene fusion status among different primary tumor foci in multifocal prostate cancers, there is concordance of TMPRSS2-ERG gene fusion status between the index tumor focus and the metastasis, suggesting that the metastasis is likely to originate from the index tumor focus.
Category: Genitourinary (including renal tumors)

Wednesday, March 24, 2010 1:00 PM

Poster Session VI # 127, Wednesday Afternoon

 

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