Comparison of CellSearch versus Parsortix circulating tumor cell enumeration and molecular characterization: A pilot study in metastatic prostate cancer patients

Prostate cancer is a leading cause of cancer death in men. Although early-stage prostate cancers can be effectively managed by surgery, radiation and/or androgen-deprivation therapies, many tumors eventually become castrate-resistant, leading to disease progression, metastasis and death. The goal of this pilot study was to gain insight into the biology of prostate cancer progression by assessing circulating tumor cells (CTCs) from 3 patient cohorts: low-volume metastatic hormone-sensitive prostate cancer (LV-mHSPC); high-volume metastatic hormone-sensitive prostate cancer (HV-mHSPC); and metastatic castrate-resistant prostate cancer (mCRPC). CTCs were assessed using the epithelial-based CellSearch assay versus an epithelial-to-mesenchymal transition (EMT)-independent Parsortix assay. CTCs were also harvested from Parsortix and assessed by downstream molecular analysis using the HyCEAD mRNA multiplex assay. Specific molecular characteristics identified through HyCEAD were compared to prostate cancer data from The Cancer Genome Atlas (TCGA). Although no significant enumeration differences were observed between the two technologies, CellSearch was able to identify a greater number of CTCs in HV-mHSPC versus LV-mHSPC patients (p≤0.05). Between the 3 patient cohorts, 17 differentially expressed genes were identified that may contribute to prostate cancer disease progression. Taken together, our findings provide a promising panel of potential biomarkers for further investigation in order to develop a comprehensive, real-time CTC liquid biopsy strategy for the personalized clinical management of metastatic prostate cancer patients in the future.