Purpose: Prostate cancer screening with PSA is plagued by high rate of unnecessary prostate biopsies, especially in the “gray zone” (4.0ng/ml – 10.0ng/ml). We introduce a new circulating-tumor-cell (CTC) biomarker for detection of prostate cancer in patients in the PSA “gray zone” level, with the clinically verified potential to substantially decrease the number of unnecessary prostate biopsies.
Materials and Methods: A total of 97 patients underwent routine prostate screening including PSA testing and DRE. One tube of blood was drawn for each patient and sent for CTC analysis in a double blinded study. A subset of 23 patients with PSA in the 4.0ng/ml – 10.0ng/ml range was selected with consent to undergo prostate biopsy for comparison with blinded CTC test results. The CTC test utilized a microfluidic platform with EpCAM as capture antibody. Suspected CTCs were eluted to a membrane chip and immunofluorently stained with CK18, PSMA and CD45 antibody to confirm. Positive CTCs are defined as CK18+ or PSMA+ and CD45-.
Results: Prostate cancer was confirmed by biopsy in 60 out of 97 patients. CTC assay reported 83% of the cancer cases, demonstrating prostate cancer detection ability of the assay. In the subset category of 23 patients (PSA in the 4.0ng/ml – 10.0ng/ml range, and prostate biopsy), the CTC assay was able to detect cancer in 100% of the prostate cancer cases.
Conclusion: This CTC-based blood test is a valuable new tool in effective screening for prostate cancer. We have demonstrated that this new CTC biomarker is able to reduce unnecessary invasive prostate biopsies in the PSA “gray zone” by over 60%, with the potential to reduce cost to the system and reduce complication rates due to prostate biopsies, thus improving patient outcomes.