MP28-02 QUANTITATIVE MEASUREMENT OF PTEN LOSS IMPROVES RISK ASSESSMENT IN PROSTATE CANCER

INTRODUCTION AND OBJECTIVES:Loss of the PTEN tumor suppressor is a powerful prognostic biomarker in prostate cancer. However, the significance of tumour heterogeneity and partial loss are not clearly defined, nor are interactions between PTEN loss and the TMPRSS2-ERG fusions, the most common genetic aberration found in prostate cancer. Taking into account TMPRSS2-ERG status, we aimed to define and quantify patterns of PTEN loss that best account for the risk of recurrence in low and intermediate-risk prostate cancer patients who underwent radical prostatectomy.METHODS:Tissue microarrays comprising a training (n=410) and validation (n=272) cohorts were constructed and PTEN protein levels were measured using automated clinical grade immunohistochemistry assays. PTEN loss was quantified per cancer cell and per cancer core using digital and visual scoring. Thresholds for PTEN loss were determined by log-rank statistics and Kaplan-Meier survival estimator. Cox’s proportional hazards models were used to determi...