[978] Assessment of TMPRSS2:ERG (T:E) Gene Fusion in Prostatic Adenocarcinomas with Mixed Acinar (PCA-A) and Ductal (PCA-D) Components: Comparison of ERG Break-Apart and T:E Fusion Probes

C Sherer, K Cieply, A Liang, A Perepletchikov, A Parwani, R Dhir, T McHale, J Salvatore, L Niemeier, S Bastacky. University of Pittsburgh, Pittsburgh, PA

Background: T:E fusion is present in many PCAs. Most studies have used an ERG break-apart probe to assess ERG disruption as a surrogate marker of T:E fusion. A T:E fusion probe assay is now available to directly assesses T:E fusion. The aim of this study was to compare both methods in pts with PCA (A+D).
Design: Formalin-fixed, paraffin-embedded sections from 19 PCA pts and 9 organ donor prostates (ODP) were obtained from the tissue bank of the University of Pittsburgh. Dxs were confirmed prior to ERG and T:E FISH. All pts had PCA (A+ D) on initial bxs (n=5) or resections (n=14), and some had benign prostate tissue (BPT). PCA-A, PCA-D, and BPT were targeted. Dual-color FISH using either a break-apart probe for ERG disruption or separate probes assessing T:E fusion were compared. Cases were positive if > 20% of cells had ERG disruption or T:E fusion, with thresholds based on ODPs.
Results:

Table 1: Comparison of ERG disruption and T:E fusion assays vs PCA and PCA subtypes

	PCA (A or D)	PCA-A	PCA-D	PCA (A+D)	BPT
ERG (+/total cases (%))	14/19 (74%)	9/16 (56%)	14/19 (74%)	9/16 (56%)	3/10 (30%)*
TE (+/total cases (%))	15/19 (79%)	11/17 (65%)	9/15 (60%)	7/11 (64%)	0/18 (0%)
p-value	> 0.05	> 0.05	> 0.05	> 0.05	> 0.05

* 1 borderline case

Mean/SD/range % + cells was: ERG+ (PCA-A(41/31/9-97; PCA-D(55/35/9-100); BPT(17/8/8-31) and T:E+ (PCA-A(28/15/11-55; PCA-D(30/17/7-61); BPT(11/4/6-19).

Table 2: Comparison of ERG disruption and T:E fusion assays vs Gleason score

Gleason score	ERG+	T:E+	p-value
3+4=7	4/6 (67%)	4/6 (65%)	p>0.05
4+3=7	6/8 (75%)	8/8 (100%)*	p>0.05
4+4=8	3/4 (75%)	3/4 (75%)	p>0.05
4+5=9	1/1 (100%)	1/1 (100%)	p>0.05

* 2 borderline cases


Conclusions: ERG break-apart and T:E fusion probes were equally sensitive for detecting pts with PCA (A or D) (79% and 74%), independent of Gleason score. The mean % of positive cells was higher for the ERG break-apart probe, suggesting that not all ERG disruptions lead to T:E fusion. Low-level ERG disruption / T:E fusion were present in BPT, most below threshhold levels.
Category: Genitourinary (including renal tumors)

Wednesday, March 24, 2010 1:00 PM

Poster Session VI # 126, Wednesday Afternoon