Prospective Evaluation of Clinical Outcomes Using a Multiplex Liquid Biopsy Targeting Diverse Resistance Mechanisms in Metastatic Prostate Cancer.

Nearly all men with prostate cancer treated with androgen receptor (AR) signaling inhibitors (ARSIs) develop resistance via diverse mechanisms including constitutive activation of the AR pathway, driven by AR genomic structural alterations, expression of AR splice variants (AR-Vs), or loss of AR dependence and lineage plasticity termed neuroendocrine prostate cancer. Understanding these de novo acquired ARSI resistance mechanisms is critical for optimizing therapy.

A novel liquid biopsy technology was used to collect mRNA from circulating tumor cells (CTCs) to measure expression of AR-Vs, AR targets, and neuroendocrine prostate cancer markers. An institutional review board-approved prospective cohort (N = 99) was used to identify patterns of gene expression. Two prospective multicenter phase II clinical trials of ARSIs for men with castration-resistant prostate cancer ( NCT01942837 [enzalutamide, N = 21] and NCT02025010 [abiraterone, N = 27]) were used to further validate these findings.

Hierarchical clustering of CTC transcripts identified two distinct clusters. Cluster 2 (C2) exhibited increased expression of AR-regulated genes and was associated with worse overall survival (median 8.6 v 22.4 months; P < .01; hazard ratio [HR] = 3.45 [1.9 to 6.14]). In multivariable analysis, C2 was prognostic independent of other clinicopathologic variables. AR-V status was not significant when accounting for C2. Upon further validation in pooled multicenter phase II trials, C2 was associated with worse overall survival (15.2 months v not reached; P < .01; HR = 8.43 [2.74 to 25.92]), prostate-specific antigen progression-free survival (3.6 v 12 months; P < .01; HR = 4.64 [1.53 to 14.11]), and radiographic progression-free survival (2.7 v 40.6 months; P < .01; HR = 4.64 [1.82 to 17.41]).

We demonstrate that a transcriptional profile detectable in CTCs obtained from liquid biopsies can serve as an independent prognostic marker beyond AR-V7 in patients with metastatic prostate cancer and can be used to identify the emergence of multiple ARSI resistance mechanisms. This is currently being investigated in additional prospective trials.

Journal of clinical oncology : official journal of the American Society of Clinical Oncology. 2021 Jul 01 [Epub]

Jamie M Sperger, Hamid Emamekhoo, Rana R McKay, Charlotte N Stahlfeld, Anupama Singh, Xinyi E Chen, Lucia Kwak, Cole S Gilsdorf, Serena K Wolfe, Xiao X Wei, Rebecca Silver, Zhenwei Zhang, Michael J Morris, Glenn Bubley, Felix Y Feng, Howard I Scher, Dana Rathkopf, Scott M Dehm, Toni K Choueiri, Susan Halabi, Andrew J Armstrong, Alexander W Wyatt, Mary-Ellen Taplin, Shuang G Zhao, Joshua M Lang

Department of Medicine, Carbone Cancer Center, University of Wisconsin, Madison, WI., Moores Cancer Center, University of California San Diego, La Jolla, CA., Department of Urologic Sciences, Vancouver Prostate Centre, University of British Columbia, Vancouver, BC, Canada., Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA., Memorial Sloan Kettering Cancer Center and Weill Cornell Medical College, New York, NY., Beth Israel Deaconess Medical Center, Boston, MA., Division of Hematology and Oncology, Department of Medicine, Helen Diller Family Comprehensive Cancer Center, University of California San Francisco, San Francisco, CA., Departments of Laboratory Medicine and Pathology and Urology, Masonic Cancer Center, University of Minnesota, Minneapolis, MN., Duke Cancer Institute Center for Prostate and Urologic Cancers, Duke University, Durham, NC.