Expression of ERG in Prostatic Acinar Adenocarcinoma Diagnosed on TRUS-guided Biopsy and its Association with WHO Grade Group- A Prospective Observational Study

Introduction: Prostate cancer is a common malignancy affecting men and the second leading cause of cancer related death in India. Numerous molecular biomarkers have been evaluated for their potential role in predicting disease progression, their response to therapy and survival. Erythroblast Transformation Specific (ETS) related Gene (ERG) is one of the newest addition in the existing list of biomarkers of prostate cancer.

Aim: To analyse the expression of ERG in prostatic adenocarcinoma and to evaluate its association with World Health Organisation (WHO) grade group.

Materials and Methods: This was a prospective observational study was conducted in the Department of Pathology in association with Department of Urology, IPGME&R, SSKM Hospital, Kolkata, West Bengal, India. The duration of the study was 1.5 years, from January 2019 to June 2020. A total of 267 cases of Transrectal Ultrasound (TRUS) guided tru-cut biopsy was included. Clinical data including preoperative Prostate Specific Antigen (PSA) level, Digital Rectal Examination (DRE) were obtained. Histopathological reports were prepared by two pathologists along with Gleason scoring and WHO grading as per 2014 International Society of Urological Pathology (ISUP) consensus conference on gleason grading of prostatic carcinoma. Formalin Fixed Paraffin Embedded (FFPE) sections of representative blocks of each tumour was selected for Immunohistochemistry (IHC) study. Only the cases which had more than 10% nuclear staining were considered as positive. Statistical analysis was performed with help of Epi Info (TM) 7.2.2.2 and Chi-square test was used to test the association of different study variables.

Results: The mean age of the study participants was 65.55 years, and the age range was 45-93 years. Among the 80 malignant cases where, ERG immunostaining was assessed, 28 cases (35%) showed positive expression. Among these positive cases, 50% cases were weakly positive, 28.57% showed moderate positivity and 21.43% had strong positive expression. Highest positivity was observed in WHO grade group V (44.83%). The intensity of ERG expression was also higher in high grade group (13) than low grade group cancer patients.

Conclusion: ERG expression in the prostate cancer can be a prognostic factor as the expression and intensity of expression both increases with higher grade group of cancer.