Improved detection of circulating tumor cells in non-metastatic high-risk prostate cancer patients

TLDR

Blood‑based assays for monitoring minimal residual disease in non‑metastatic prostate cancer are not yet clearly established. The study aims to demonstrate that clinically relevant circulating tumor cells can be detected using existing technologies. The authors combined CellSearch, CellCollector, and EPISPOT assays on peripheral blood from high‑risk prostate cancer patients before and three months after radical prostatectomy to enhance CTC detection. The combined assay approach detected CTCs in 81.3 % of patients, with 21.5 % having ≥5 CTCs/7.5 ml; CTCs fell significantly after surgery, and EPISPOT positivity correlated with PSA levels and tumor stage.

Abstract

The relevance of blood-based assays to monitor minimal residual disease (MRD) in non-metastatic prostate cancer (PCa) remains unclear. Proving that clinically relevant circulating tumor cells (CTCs) can be detected with available technologies could address this. This study aimed to improve CTC detection in non-metastatic PCa patients by combining three independent CTC assays: the CellSearch system, an in vivo CellCollector and the EPISPOT. Peripheral blood samples from high-risk PCa patients were screened for CTCs before and three months after radical prostatectomy (RP). Combining the results of both time points, CTCs were detected in 37%, 54.9% and 58.7% of patients using CellSearch, CellCollector and EPISPOT, respectively. The cumulative positivity rate of the three CTC assays was 81.3% (87/107) with 21.5% (23/107) of patients harboring ≥5 CTCs/7.5 ml blood. Matched pair analysis of 30 blood samples taken before and after surgery indicated a significant decrease in CTCs captured by the CellCollector from 66% before RP to 34% after therapy (p = 0.031). CTC detection by EPISPOT before RP significantly correlated with PSA serum values (p < 0.0001) and clinical tumor stage (p = 0.04), while the other assays showed no significant correlations. In conclusion, CTC-based liquid biopsies have the potential to monitor MRD in patients with non-metastatic prostate cancer.