Prognostic Significance of Circulating Tumor Cell Count in Patients With Metastatic Hormone-sensitive Prostate Cancer

Abstract

To analyze the correlation between circulating tumor cell (CTC) levels and clinicopathologic parameters (prostate-specific antigen level, Gleason score, and TNM stage) in patients with metastatic hormone-sensitive prostate cancer (PCa) and to establish its prognostic value in overall survival (OS) and progression-free survival (PFS). A prospective, 3-arm study was performed that included 30 patients with localized PCa; 30 patients with metastatic PCa, and 30 healthy volunteers. A single 7.5-mL peripheral blood sample was taken. The CTCs were isolated using an immunomagnetic method based on the CellSearch system. Kendall's tau and Spearman's rho coefficients of correlation were used. The multivariate Cox regression model addressed OS and PFS. The median follow-up was 42.9 months (interquartile range 27.14-49.5). A significant positive correlation was demonstrated between the CTC level and all tumor burden markers (prostate-specific antigen and T, N, and M stage; P <.001), except for Gleason score (tau = 0.16). A cutoff of ≥ 4 CTCs/7.5 mL was chosen to distinguish patients with a poor prognosis. These patients had a significantly shorter median OS and PFS (24 vs 45 months and 7 vs 44 months, respectively; P <.001). As the CTC level increased, the OS and PFS decreased. The risk of mortality and progression for the patients with ≥ 4 CTCs was 4.1 (P = .029) and 8.5 (P <.001) times greater. Multivariate analyses indicated that a CTC of ≥4 was an independent prognostic factor for PFS (hazard ratio 5.9, P <.005). The CTC count in peripheral blood could provide a method of staging PCa correctly and be of value when assessing the prognosis of metastatic hormone-sensitive PCa.