Development Of New, Sensitive Assay For Circulating Tumor Cell Detection In Prostate Cancer.

e15015 Background: Circulating tumor cells (CTC) have emerged as a valuable cancer biomarker. When measured by the FDA-approved CellSearch CTC Kit from Veridex, the number of CTCs in the peripheral blood correlates with the overall and progression free survival in patients with metastatic prostate, breast, and colorectal cancers. Here, we further evaluated the association of CTCs with conventional biomarkers that measure disease burden in prostate cancer patients and developed methodology to increase the CTC yield for molecular profiling. Methods: We investigated CTCs obtained from 35 men with metastatic hormone refractory prostate cancer. CTCs were isolated from blood using the CellSearch CTC Kit, which immunomagnetically isolates EpCAM+ cells and enumerates CK+/DAPI+/CD45- cells. The association between CTC number and PSA, alkaline phosphatase or LDH were analyzed using Spearman correlation method. To increase the CTC recovery, we validated the CellSearch CTC Profile Kit, which allows to recover EpCAM+ cells and enumerate CTCs using Laser Scanning Cytometry (LSC) analysis. FISH for PTEN, TMPRSS-ERG and AR was performed on CTCs. Results: Fifteen patients (43%) had zero CTCs and 20 (57%) had one or more CTCs, as measured with CellSearch CTC Kit. CTCs correlated with conventional biomarkers such as mean PSA (p=0.038), mean alkaline phosphatase (p=0.035), and mean LDH (p<0.0001). The CTC Profile Kit allowed isolation of CTCs from the CTC-negative (as detected by standard kit) samples and yielded higher CTC counts (range 0 to 56 vs. 14 to 180). Increased recovery permitted the re-localization of CTCs to determine the status of PTEN, TMPRSS-ERG and AR deletion, fusion or amplification by FISH. Conclusions: Our results indicate that CTC counts correlate with standard markers of prostate cancer. Further, the CellSearch Profile Kit permits higher yield of CTC isolation thus enabling molecular characterization of CTCs. Author Disclosure Employment or Leadership Position Consultant or Advisory Role Stock Ownership Honoraria Research Funding Expert Testimony Other Remuneration ApoCell, Inc.