Background: EN2 is part of the HOX gene family and plays a role in foetal development. More recently a potential oncogenic role for the protein has been postulated and its utility as a cancer biomarker has been explored in prostate cancer (PrCa) and breast cancer. Carriers of mutations in the BRCA1 and BRCA2 genes have an increased risk of PrCa (1.8-fold and 5-fold respectively) and their tumours tend to be more aggressive and advanced than sporadic cases. Currently there is no national screening program for BRCA mutation carriers in the UK, and the IMPACT study was set up to evaluate PSA screening in this particular group. Here we analyse the efficacy of the urinary EN2 protein as a marker of early cancer detection within this higher risk group. Methods: First pass urine (without preceding digital rectal examination) was collected as part of the IMPACT screening study which enrolled individuals aged between 40 and 69 who were unaffected by PrCa at time of enrolment into the study (n= 418). All participants were from families harbouring a BRCA1 or BRCA2 mutation and were either BRCA mutation carriers themselves or controls with a negative predictive BRCA genetic test. They underwent annual PSA test with a PSA of > 3.0 ng/ml triggering a diagnostic biopsy. EN2 protein was measured in the urine using an ELISA; (positive = > 42.5ng/ml). Results: Our initial results demonstrated urinary EN2 had a sensitivity of 66.67% and a specificity of 89.29% when discriminating which men had been diagnosed with PrCa; the ROC AUC was 0.816. The difference in EN2 level between those diagnosed with cancer and those who were not was significant (p = <0.001). There was trend towards higher EN2 levels in those with more aggressive tumours (median EN2 84.5ng/mL in Gleason ≤3+4 vs 111ng/mL in Gleason ≥4+3), however this was not statistically significant. In one PrCa case EN2 rise preceded PSA rise by 2 years. Further samples are in the process of being analysed, results from these will be included. Conclusions: Urinary EN2 protein measurement warrants further investigation as a PrCa biomarker in this higher risk group with genetic predisposition to PrCa.