Circulating tumor cell quantification during abiraterone plus prednisone therapy may estimate survival in metastatic castration-resistant prostate cancer patients.

Abstract

Circulating tumor cells (CTCs) predict survival in response to different interventions in metastatic castration-resistant prostate cancer (mCRPC) patients. This study aimed to explore the dynamic change in CTCs during abiraterone plus prednisone therapy and its optimal threshold for prognostication in mCRPC patients. CTCs in blood samples from mCRPC patients (N = 98) at baseline and in the 2nd month after abiraterone plus prednisone treatment initiation (M2) were enumerated by using the CellSearch System. CTCs were detected in 64.8% of mCRPC patients at baseline with a median value (interquartile range) of 2.0 (0.0-4.0). Elevated CTC count was related to visceral metastasis (P = 0.003), high alkaline phosphatase (P = 0.043), and high lactate dehydrogenase (P = 0.007). Baseline CTC ≥ 1 (vs. < 1) was only associated with shortened radiographic progression-free survival (rPFS) (P = 0.043); additionally, baseline CTC ≥ 5 (vs. < 5) was linked with unfavorable rPFS (P = 0.037) and overall survival (OS) (P = 0.021). Following the therapy, CTCs were reduced at M2 (P < 0.001). Notably, CTC ≥ 1 (vs. < 1) (P = 0.002) and CTC ≥ 5 (vs. < 5) (P < 0.001) at M2 were related to shortened rPFS according to the Kaplan‒Meier curves, and they could independently estimate deteriorative rPFS in the multivariate Cox regression (P = 0.043 and P = 0.027, respectively). Similarly, CTC ≥ 1 (vs. < 1) (P = 0.022) and CTC ≥ 5 (vs. < 5) (P = 0.002) at M2 were related to shortened OS, whereas only CTC ≥ 5 (vs. < 5) could independently predict unfavorable OS (P = 0.017). CTC count ≥ 5 at M2 exhibits excellent prognostic value for abiraterone plus prednisone therapy in mCRPC patients.