The relevance of ERG immunoexpression intensity for prostatic adenocarcinoma in radical prostatectomy of 635 samples

Prostate cancer is the world's most frequently diagnosed malignancy in men. Recent work suggests that patients with high ERG expression intensity are significantly more likely to develop biochemical relapse and metastasis, and die of prostate cancer. The objective of this study was to determine the relationship between the intensity of ERG protein expression and the staging of prostate cancer and the formation of metastases in 635 samples. A retrospective cohort analysis was performed using immunohistochemistry reactions in tissue microarray samples taken from non-neoplastic and neoplastic prostate tissue from patients who underwent radical prostatectomies at a reference hospital from 2009 to 2016. For the ERG marker analysis, the samples were scored for the presence or absence of nuclear signals. Weak, moderate, or strong intensity of the nuclei of the observable tumor cells was considered to be positive markers. All told, 635 samples were evaluated, and the ERG expression was inconclusive in 9% of cases, while 30% were positive and 61% were negative. Of the samples with positive result: 25.8% were weak and focal, 53.2% were moderate, and 21% were strong. Finally, 21% of the cases with a positive ERG had a high Gleason score. Metastasis was detected in 41% of the patients who were ERG positive, and of these, the majority had moderate marking and were aged older than 60 years, although there was no statistically significant difference between the older and younger age groups. Patients with moderate to strong ERG staining had higher staging compared to the others, and no increase in metastasis was detected in patients with more intense ERG expression. More studies should be carried out to corroborate these results and to reach a consensus on the intensity and scoring of the expression levels of ERG markers.