Prevalence of TMPRSS2-ERG fusion prostate cancer among men undergoing prostate biopsy in the United States

Abstract

Purpose: Fusion of the TMPRSS2 prostate-specific gene with the ERG transcription factor is a putatively oncogenic gene rearrangement that is commonly found in prostate cancer tissue from men undergoing prostatectomy. However, the prevalence of the fusion was less common in samples of transurethral resection of the prostate from a Swedish cohort of patients with incidental prostate cancer followed by watchful waiting, raising the question as to whether the high prevalence in prostatectomy specimens reflects selection bias. We sought to determine the prevalence of TMPRSS2-ERG gene fusion among prostate-specific antigen-screened men undergoing prostate biopsy in the United States.

Experimental design: We studied 140 prostate biopsies from the same number of patients for TMPRSS2-ERG fusion status with a fluorescent in situ hybridization assay. One hundred and thirty-four samples (100 cancer and 34 benign) were assessable.

Results: ERG gene rearrangement was detected in 46% of prostate biopsies that were found to have prostate cancer and in 0% of benign prostate biopsies (P < 0.0001). Evaluation of morphologic features showed that cribriform growth, blue-tinged mucin, macronucleoli, and collagenous micronodules were significantly more frequent in TMPRSS2-ERG fusion-positive prostate cancer biopsies than gene fusion-negative prostate cancer biopsies (P < or = 0.04). No significant association with Gleason score was detected. In addition, non-Caucasian patients were less likely to have positive fusion status (P = 0.02).

Conclusions: This is the first prospective North American multicenter study to characterize TMPRSS2-ERG prostate cancer prevalence in a cohort of patients undergoing needle biopsy irrespective of whether or not they subsequently undergo prostatectomy. Our results show that this gene rearrangement is common among North American men who have prostate cancer on biopsy, is absent in benign prostate biopsy, and is associated with specific morphologic features. These findings indicate a need for prospective studies to evaluate the relationship of TMPRSS2-ERG rearrangement with clinical course of screening-detected prostate cancer in North American men, and a need for the development of noninvasive screening tests to detect TMPRSS2-ERG rearrangement.

Figure 1

Morphological features associated with a positive TMPRSS2-ERG fusion status in prostate cancer. A: Prostate cancer Gleason pattern 3 showing blue-tinged mucin. Inset picture shows FISH image of representative nucleus. One yellow and one red signal are present, demonstrating the presence of TMPRSS2-ERG fusion through deletion. B: Prostate cancer Gleason pattern 3 showing macronucleoli. The inset picture in the upper left corner shows the macronucleoli in the boxed area, and the inset picture in the upper right corner shows a FISH image of representative nuclei. One yellow and one red signal are present in each nucleus, demonstrating the presence of TMPRSS2-ERG fusion through deletion. C: Prostate cancer Gleason pattern 4 with collagenous micronodules. Inset pictures shows FISH image of representative nuclei. One yellow, and separate red and green signals are present in each nucleus, demonstrating the presence of TMPRSS2-ERG fusion through insertion. D: Prostate cancer Gleason pattern 4 with cribriform growth pattern. Inset picture shows FISH image of representative nucleus. One yellow and separate red and green signals are present, demonstrating the presence of TMPRSS2-ERG fusion through insertion. Original magnification of H&E images, 20× objective (A and B), and 10× objective (C and D). Original magnification of FISH images, 60× objective.