Objective: To determine the prevalence and prognostic value of ERG in prostatic cancer. The association of ERG status and other clinic-pathologic features were also studied.

Materials and Methods:  Tissue paraffin blocks of patients who had diagnosis of prostatic acinar adenocarcinoma during 2006 to 2013 at Faculty of Medicine Vajira Hospital were identified. The original H&E stained slides were reviewed to select 2 areas with the most prominent Gleason pattern for tissue sampling. The selected tissue samples were embedded in tissue microarray (TMA) blocks and processed for ERG staining. Intensity and area of positive ERG stain were evaluated independently by two pathologists. Clinico-pathological data collected were age, preoperative prostate-specific antigen (PSA), tumor stage, PSA biochemical-relapse, and pathological information of peri-neural or lymphovascular invasion, surgical margin, the International Society of Urological Pathology (ISUP) grade group, and Gleason score were collected and analyzed.

Results: Among 107 samples, positive ERG staining was found in 31.8% (34 cases). Features which were significantly associated with ERG positive comparing to those in ERG negative were: younger age, 67.7 ± 8.5 years vs 72.6 ± 8.6 years (p = 0.008); lower Gleason score (6 and 7), 79.4% (27 cases) vs 20.6% (7 cases) (p = 0.010) and lower ISUP grade group (group 1, 2 and 3), 82.4% (28 cases) vs 17.6% (6 cases) (p = 0.004), respectively. No significant different association between ERG status and other clinic-pathologic features including survivals. The 5-year overall survival and 5-year disease-free survival (95% confidence intervals) of the patients with ERG positive and negative were: 84.4% (70.1-98.7%) vs 77.1% (66.1-88.1%) (p = 0.399) and 77.4% (60.9-93.9%) vs 78.2% (67.6-88.8%) (p = 0.571), respectively.

Conclusion: The prevalence of ERG-positive in prostate cancer patients was 31.8%. The patients with ERG positive had younger age, more of low Gleason score and low ISUP grade group. No significant association between ERG status and other clinic-pathologic parameters as well as survivals were found.