Characterization of circulating tumor cells in patients with localized high risk prostate cancer, post-prostatectomy.

Abstract

110 Background: Approximately 15% of men with newly diagnosed prostate cancer (PCa) have high-risk features, many of these patients will recur despite definitive therapy. Better predictive biomarkers could allow for earlier detection of recurrence and change surveillance paradigms. The role of circulating tumor cells (CTCs) as biomarkers in this context is not well defined. Here, we evaluate the ability to detect CTCs from men with high risk, localized PCa after radical prostatectomy (RP) and correlate their presence with prospective clinical data. Methods: Blood samples from 31 patients with high risk, localized PCa were obtained 2-4 months post RP and sent to Epic Sciences on an IRB approved protocol. Nucleated cells were subjected to immunofluorescent (IF) staining for cytokeratin (CK), CD45, and AR N-terminus. CTCs were identified by fluorescent scanners using algorithmic analysis. Cytokeratin expressing (CK+) CTCs were enumerated and subsequently analyzed for AR expression and individually sequenced for copy number variation (CNV) and large scale transitions (LST, a surrogate of genomic instability). Patients were followed prospectively for biochemical recurrence, defined as detectable PSA. Progression free survival (PFS) was calculated using Kaplan-Meier and Cox proportional hazards. Results: CTCs were detected in 87.1% (27/31) samples with an average of 5.6 CTCs/ml (range: 0 – 22.87) detected per patient. AR expression was detected in 12.9% (4/31) of patients. Ninety-nine CTCs from 14 patients were amenable to LST and CNV analyses. 10.1% (10/99) CTCs from 7 patients exhibited higher ( > = 6) LSTs than control WBCs (95% WBCs had LST < 6). Copy number alterations were detected in CTCs in commonly mutated genes in PCa, including AR, MYC, and TP53 amplification and deletions in PTEN and RB1. Patients with higher CTC burdens exhibited a trend toward shorter PFS (hazard ratio: 1.65; 95% confidence interval: 0.7-3.86; p: 0.13). Conclusions: There was a high incidence of CTC detection after RP in this population using a novel platform. We observed a trend toward shorter PFS in those with higher CTC burden. Genomic alterations were detectable in CTCs and consistent with established CNAs in PCa.