Longitudinal transcriptome profiling of localized hormone-sensitive tumors in treatment-naïve ENACT patients with prostate cancer with and without enzalutamide (ENZA).

Abstract

5026 Background: The ENACT trial (NCT02799745) randomized men with low- or intermediate-risk prostate cancer to 12 months of ENZA monotherapy followed by active surveillance (AS) for 12 months or to AS alone. Men were followed longitudinally, including by serial genome-wide expression profiling. Of 258 genomic signatures evaluated from baseline samples, increased Decipher genomic classifier score was prognostic for progression on AS; androgen receptor activity (AR-A) and PAM50 subtypes were associated with clinical benefit from ENZA, as previously reported. Here we present transcriptomic changes over time for men undergoing AS and those treated transiently with ENZA. Methods: Gene-expression profiling was performed via the Decipher GRID platform (Veracyte, Inc.) on 131 ENACT patient samples (ENZA, n=57; AS, n=74) collected at prespecified time points (screening, 12 months, and 24 months). Predefined GRID signatures were assessed for correlation with biological and clinical characteristics, including immune activity, treatment sensitivity, metastatic risk, and molecular subtypes. Statistical analysis was conducted by Cox proportional hazards models and logistic/linear regression; longitudinal changes were assessed by linear mixed-effects models. Results: Analysis of 12-month longitudinal samples showed significant transcriptomic changes in patients treated with ENZA, including markers of AR-A downregulation, decreased regulatory T-cell suppression, and increased immune activation. Many of the transcriptomic signature changes that occurred during ENZA treatment, including immune marker changes, were transient and returned to baseline values by 24 months following ENZA treatment discontinuation at 12 months. Conclusions: This exploratory biomarker analysis provides valuable data on transcriptomic changes in patients undergoing AS and those exposed to ENZA followed by cessation of treatment. Longitudinal analysis data provided insights into progression of early disease in the AS arm and possible strategies for extending ENZA activity beyond progression. Immune modulation with ENZA treatment may provide further insights for exploration of immunotherapy strategies. Clinical trial information: NCT02799745 .