A 17-gene genomic prostate score as a predictor of adverse pathology for men on active surveillance.

Abstract

97 Background: The OncotypeDX Genomic Prostate Score (GPS) test is a RNA expression assay that can be performed on needle-core biopsies from men with prostate cancer (PCa). GPS has previously been validated as a predictor of adverse pathology in men with low-risk prostate cancer who undergo primary radical prostatectomy (RP). We sought to determine whether GPS was associated with increased risk of adverse pathology for men enrolled on active surveillance (AS) who undergo delayed RP. Methods: Of 1,662 men enrolled on AS at the University of California San Francisco (UCSF) who consented for prospective data collection, we evaluated 215 men on AS with Gleason score (GS) 3+3 and GS 3+4 PCa who underwent GPS testing at diagnostic or confirmatory biopsy (ie. within 1 year). Patients had at least 6 biopsy cores sampled and ≤ 33% positive cores, stage T1 or T2 disease, PSA < 20, and clinical Cancer of the Prostate Risk Assessment (CAPRA) score < 6. The primary outcome was adverse pathology at delayed RP, defined as GS ≥ 4+3, stage ≥ pT3a or pN1. We performed Cox proportional hazards regression, and inverse probability censored weights (IPCW) models to evaluate association between GPS and adverse pathology, adjusting for CAPRA score. Results: 72 percent (N=154) of the cohort had GS 3+3, and 28 percent (N=61) had GS 3+4. 83 percent of men (N=179) were low risk, and 17 percent of men (N=36) were intermediate risk by CAPRA scoring. Median GPS was 26.4 (interquartile range [IQR]: 18.8, 34.6). Median time from diagnosis to RP was 23 months (IQR: 15, 40). 121 men had adverse pathology on delayed RP at a median time of 27 months (IQR 16, 43) to prostatectomy. In a Cox-proportional hazards regression adjusted for CAPRA, GPS was associated with increased risk of adverse pathology at delayed RP (Hazard Ratio [HR] per 5 units: 1.12, 95 Confidence Interval [CI]: 1.05, 1.20, p < 0.01). CAPRA score was not associated with adverse pathology (p=0.09). IPCW model findings were very similar to Cox results. Conclusions: In patients who undergo RP after a relatively short period of AS, a higher GPS is associated with increased risk for adverse pathology on delayed RP.