Effect of a genomic classifier on adjuvant radiation recommendations after prostate cancer surgery.

151 Background: Clinical guidelines recommend adjuvant radiation therapy (ART) after radical prostatectomy in men with adverse pathological features. Practice patterns vary on use of ART. This prospective, multi-center study examines the effect of a genomic classifier (GC) on ART recommendations post-prostatectomy. Methods: A prospective, pre-post tumor-board–like survey was conducted to assess urologists’ treatment recommendations for ART as part of a clinical utility study; results are from a pre-specified interim analysis of 11 unique de-identified cases with adverse pathology. All case histories were based on patients treated by at least one of the urologists participating in the study. Patient age, pathological features, and preoperative prostate-specific antigen were presented to the respondents. Presentation of cases was randomized to minimize recall bias. For each case history, physician respondents first were asked to render an ART recommendation without knowledge of the GC findings (pre-GC); they were then asked to render an ART recommendation after GC findings were provided for the same cases (post-GC). Recommendations were made without knowledge of others’ responses. Results: Twelve urologists at 11 US institutions provided 132 adjuvant therapy recommendations. Pre-GC, ART was recommended in 56 (42%) cases. Thirty three percent (95% CI: 25-41%) of recommendations changed following review of GC results. Among pre-GC recommendations for ART, 39% (95% CI: 27-53%; n=22) changed to observation and among pre-GC recommendations for observation, 8% (95% CI: 3%-17%; n=5) changed to ART. Compared to observation, ART was 11.8 times (odds ratio 95% CI: 2.9 - 46.3) more likely to be recommended for cases with high risk GC scores. Adjuvant therapy recommendations were more strongly influenced by GC score (p=0.0006) than any clinical variable (all p>0.33) when both informed recommendations. Conclusions: Additional knowledge of the tumor’s genomic characteristics, as assessed by GC, results in a statistically significant and clinically meaningful change in treatment recommendations in patients indicated for adjuvant radiation therapy by current clinical guidelines.