1378P Biopsy-based basal-luminal subtyping classifier in high-risk prostate cancer: Analysis of the NRG Oncology/RTOG 9202, 9413, and 9902 randomized phase III trials

Subtype differentiation in prostate cancer (PCa) has been shown to be prognostic and predictive of androgen deprivation therapy (ADT) response the postoperative setting. We sought determine whether basal-luminal subtypes based on gene expression profiling pretreatment biopsy samples would for benefit long- (LT; 24-28 months) vs short-term (ST; 4 ADT, hypothesizing that patients with basal tumors more from longer term ADT. Whole-transcriptome arrays enrolled NRG/RTOG 9202, 9413, 9902 randomized phase III trials were analyzed. The ability a 215 subtyping classifier (PSC) was evaluated biochemical failure (BF), distant metastasis (DM), metastasis-free survival (MFS), cancer-specific mortality (PCSM), overall (OS) multivariable Cox models (MVA). Event rates estimated by cumulative incidence method compared Gray’s or logrank tests. 265 analyzed (40% PSC basal, 60% luminal). In MVA, subtype had worse prognosis luminal MFS (HR [95% CI] 1.8 [1.3-2.5], p<0.001), PCSM 2.8 [1.5-5.0], OS [1.3-2.6], p<0.001). at 10 years 26% (95% CI 17-35%) 11% (6-15%) subtypes. A significant interaction between ADT duration observed BF (p=0.02) (p=0.007). Similar but non-significant trends DM, MFS, OS. Basal significantly benefitted LT- STADT (10-year 5% 0-11%] 42% [29-56%], while outcomes did not differ (p=0.72). Gene analysis three NRG high-risk PCa suggests is STADT. Patients those not, supporting hypothesis can help personalize PCa.