Identification and characterization of circulating tumor cells in post prostatectomy patients with localized high risk prostate cancer.

Abstract

69 Background: Over 15% of men with newly diagnosed prostate cancer (PCa) have high-risk features that raise the recurrence risk. Better biomarkers could allow for even earlier detection of biochemical recurrence (BCR) and inform adjuvant treatment decisions. Circulating tumor cells (CTCs) may represent the earliest form of metastases, however their role as biomarkers in men with localized PCa is not well defined. Here, we aim to enumerate and molecularly and genomically analyze CTCs using an enrichment-free, unbiased CTC identification technology from men with high-risk, localized PCa after radical prostatectomy (RP) and correlate the analysis with clinical outcomes. Methods: Blood samples from 37 patients with high-risk, localized PCa were obtained 2-5 mos post RP and shipped to Epic. All nucleated cells were subjected to immunofluorescent staining for cytokeratin (CK), CD45, and AR. CTCs were identified using algorithmic analysis. CK+ CTCs were enumerated and subsequently analyzed for AR expression and individually sequenced for copy number alterations (CNA). Patients were followed for BCR, defined as detectable PSA > 0.2ng/dL. Progression free survival (PFS) was calculated using Kaplan-Meier and Cox proportional hazards. Results: CTCs were detected in 81.1%(30/37) of patients with an average of 5.2 CTCs/ml (range: 0 – 22.9) detected per patient. AR expression was detected in 18.9% (7/37) of patients. Ninety nine CTCs from 14 patients were picked and sequenced. CNAs were identified in CTCs in commonly mutated genes in PCa, including MYC amplification and CHD1 deletions. Patients with higher traditional CTC (CK+) burdens exhibited a trend towards 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 patients with high-risk, localized PCa. A trend toward shorter PFS was seen in those with higher CTC burden. Genomic alterations were detectable in CTCs and consistent with established CNAs in PCa. With further testing in appropriately powered cohorts early CTC detection after primary therapy could represent an informative biomarker to stratify patients with high risk PCa.