Objective: To validate the 17-gene Oncotype DX Genomic Prostate Score (GPS) biopsy-based gene expression assay as a predictor of adverse pathology (AP, Gleason score [pGS] ≥4+3 and/or ≥pT3) in a prospectively enrolled cohort. Methods: Between July 2014 and September 2015, 1200 men with very low-, low-, and favorable intermediate-risk prostate cancer enrolled in a multi-institutional prospective study of the GPS assay (NCT03502213). The subset who proceeded to immediate radical prostatectomy (RP) after GPS testing was included in a prespecified subanalysis of GPS on biopsy and its association with surgical AP on RP using logistic regression and receiver operating characteristic curves. The effect of GPS testing on physicians’ and patients’ attitudes about decision making was assessed with the Decisional Conflict Scale. Results: One hundred fourteen patients (treated by 59 physicians from 19 sites) elected RP and 40 (35%) had AP. GPS result was a significant predictor of AP (odds ratio per 20 GPS units [OR/20 units]: 2.2; 95% CI 1.2-4.1; P =.008) in univariable analysis and remained significant after adjustment for biopsy Gleason score, clinical T-stage, and logPSA (OR/20 units: 1.9; 95% CI 1.0-3.8; P =.04), or NCCN risk group (OR/20 units: 2.0; 95% CI 1.1-3.7; P =.02). Mean pre-GPS Decisional Conflict Scale score was 27 (95% CI 24-31), which improved significantly after GPS testing to 14 (95% CI 11-17) (P <.001). Conclusion: In this real-world multi-institutional study, the GPS assay was prospectively confirmed as an independent predictor of AP at surgery. GPS testing was associated with reduced patient decisional conflict.
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