Circulating tumour cell (CTC) counts as intermediate end points in castration-resistant prostate cancer (CRPC): a single-centre experience

Background: The purpose of this study was to evaluate the association of circulating tumour cell (CTC) counts, before and after commencing treatment, with overall survival (OS) in patients with castration-resistant prostate cancer (CRPC). Experimental design: A 7.5ml of blood was collected before and after treatment in 119 patients with CRPC. CTCs were enumerated using the CellSearch®System. Results: Higher CTC counts associated with baseline characteristics portending aggressive disease. Multivariate analyses indicated that a CTC ≥5 was an independent prognostic factor at all time points evaluated. Patients with baseline CTC ≥5 had shorter OS than those with 30 months, hazard ratio (HR) 3.25, P = 0.012]; patients with CTC >50 had a poorer OS than those with CTCs 5–50 (median OS 6.3 versus 21.1 months, HR 4.1, P < 0.001). Patients whose CTC counts reduced from ≥5 at baseline to