645 PROGNOSTIC SIGNIFICANCE OF THE QUANTIFICATION OF CIRCULATING TUMOR CELLS IN PATIENTS WITH METASTATIC HORMONO-SENSITIVE PROSTATE CANCER

INTRODUCTION AND OBJECTIVES: Analysis of the relationship between circulating tumor cells (CTC) levels with the clinicalpathologic parameters (PSA levels, Gleason score and TNM staging) in patients with metastatic hormone-sensitive prostate cancer (PC) and establish his prognostic value in the overall and progression-free survival. METHODS: Prospective, three arms, study: 26 patients (p) with localized PC (Stage I–II)(LPC); 30p with metastatic PC (Stage IV) (MPC) and 30 healthy volunteers. A single 7.5 ml sample of peripheral blood was taken, CTCs were isolated using and immunomagnetic method based on the CellSearch system (Veridex). CTCs were identified as nucleated cells negative for CD45 (leukocytes) and positive for cytokeratins. (8, 18 y 19). RESULTS: The median of follow-up was 42.9 months (27.14– 49.5). Patients with MPC had significantly higher CTC levels [m: 18.5 (1–126)] compared with the other two groups (P 0.001). A significant positive correlation was demonstrated (P 0.001) between CTC levels and all tumour burden markers: PSA (Rho 0.55), T (Tau 0.47), N (m N1: 18.5, m N0: 0.0) and M ( Tau 0.54) except Gleason score(Tau 0.16). The overall survival to 6, 12 and 18 months was 80 %, 69 % and 62 % respectively. The progression-free survival to 6, 12 and 18 months was 76 %, 46 % and 33 % respectively. A cutoff level 4 CTC (S: 90 %; E: 87.6 %) was chosen to distinguish patients with an unfavorable prognosis. These patients had a significantly shorten median overall and progression-free survival (P 0.001). As the CTC levels were increasing, the overall survival and progression-free survival decreased. The risk of mortality and progression for the patients with 4 CTC was 4.1 (IC 95 %: 1.1–14.6; P 0.029) and 8.5 (IC 95 %: 2.6–26.9; P 0.001) times higher. Using a multivariate piecewise Cox regression mode, the level of 4 CTC was an independent predictor of PSA relapse(HR: 5,9; IC 95 %: 1,7-20,4; p 0,005). CONCLUSIONS: The inmunomagnetic analysis allows us to quantify the CTC in peripheral blood and could provide a possibility for correctly staging and to estimate the prognostic value of the metastatic hormone-sensitive prostate cancer with the purpose of the early onset of new therapies.