Development and clinical validation of a novel biopsy-based six-gene signature to accurately risk-stratify men with early-stage prostate cancer to aid treatment decision making.

Abstract

374 Background: Prostate cancer (PCa) is diagnosed in over 1.2 million men worldwide annually, making it the second-most common non-cutaneous cancer in men. Most men have indolent PCa and can safely defer treatment with active surveillance. However, many patients are commonly treated with surgery (radical prostatectomy, RP) or radiation therapy, which are associated with a significant reduction in quality of life. Molecular signatures have been developed to assist clinicians in stratifying patients based on their risk of aggressive PCa; while these have shown promise, there remains a significant opportunity for improving prognostic capacity. Methods: A panel of fourteen prognostic genes was identified from The Cancer Genome Atlas Prostate Adenocarcinoma (TCGA PRAD) database. Gene expression was measured by reverse-transcription quantitative polymerase chain reaction in RP samples from an Irish cohort of men diagnosed with PCa and treated with RP (PCRC, n=426). Cross-validated logistic regression analysis identified a six-gene molecular risk score (MRS) with strong prognostic performance to predict aggressive PCa, i.e., adverse pathology (AP) at RP or biochemical recurrence (BCR). The MRS was combined with the Cancer of the Prostate Risk Assessment (CAPRA) score to create a molecular plus clinical risk score (MCRS). The MRS and MCRS were clinically validated in biopsy samples from an independent Swedish cohort of men diagnosed with PCa and treated by RP (UPCA, n=100). Results: We identified a six-gene signature, consisting of four prognostic and two reference genes, with improved prognostic value over clinical features. In the clinical biopsy validation study univariable analysis, the AUC of the signature for AP was 0.72 (MRS) and 0.82 (MCRS) versus 0.72 for EAU risk categories and 0.82 for CAPRA. The C-index for BCR was 0.62 (MRS) and 0.74 (MCRS) versus 0.65 for EAU risk categories and 0.73 for CAPRA. Furthermore, in bivariable analysis, the six-gene signature added statistically significant (p < 0.001) prognostic value to EAU risk categories and CAPRA. Conclusions: The six-gene prognostic signature has strong performance for AP and BCR in an independent clinical biopsy validation study. MCRS can provide improved prognostic stratification and inform optimal patient management post-diagnosis.