Detection and oncological impact of circulating tumor cells in bladder cancer patients with presence of copy number variations of circulating cell free DNA.

Abstract

495 Background: To investigate detection and oncological impact of circulating tumor cells (CTC) in bladder cancer patients with presence of copy number variations (CNV) of circulating cell-free DNA (cfDNA) treated with radical cystectomy (RC). Methods: Secondary analysis of 85 bladder cancer patients, who were prospectively enrolled and treated with RC at our institution between 2011 and 2014. Blood samples were obtained preoperatively. For CTC analysis, blood was analyzed with the CellSearch system (Janssen). cfDNA was extracted from serum using the PME DNA Extraction kit (Analytik Jena). Multiplex ligation-dependent probe amplification (MLPA) was carried out to identify CNV of cfDNA. In a single reaction MLPA allows analyzing CNV in 43 chromosomal regions containing 37 genes. Results: MLPA was suitable for characterization of CNV in 72 patients (84.7%). Data on CTC was available for 45 of these patients (62.5%). In total, 7 patients (15.6%) had CTC with a median CTC count of one (IQR: 1-3). In 21 patients (46.7%), one to 6 deleted or amplified chromosomal regions were detected with a median CNV count of 2 (IQR: 1-2). Overall, most changes were located in the genes CDH1, RIPK2 and ZFHX3 in 8 patients (17.8%), 6 patients (13.3%) and 5 patients (11.1%). Chromosomal aberrations were most frequently found on chromosome 8 in 8 patients (17.8%). Overall, presence of CTC was not associated with CNV status. However, presence of CTC was associated with copy number losses in miR-15a (p = 0.011). Patients with CTC had reduced recurrence-free survival (RFS) compared to patients without CTC (p = 0.012). In combined Kaplan-Meier analysis, patients with CTC plus presence of CNV had reduced cancer-specific survival (CSS) and RFS compared to patients without CTC but with presence of CNV (p≤0.035). In addition, patients with CTC plus presence of CNV had reduced RFS compared to patients without CTC and without presence of CNV (p = 0.028). Conclusions: CTC and CNV of various genes are detectable in peripheral blood of bladder cancer patients. The presence of CTC seems to be associated with CNV of specific genes. CTC have a negative impact on survival in patients with and without presence of CNV.