Prognostic value of circulating VEGFR2 ⁺ bone marrow-derived progenitor cells in patients with advanced cancer

We hypothesised that host-related markers, possibly reflecting tumour aggressiveness, such as circulating endothelial cells (CEC) and circulating VEGFR2 ⁺ bone marrow-derived (BMD) progenitor cells, could have prognostic value in patients with advanced cancer enrolled in early anticancer drug development trials. Baseline CECs (CD45 ^-CD31 ⁺CD146 ⁺7AAD ^- cells) and circulating VEGFR2 ⁺-BMD progenitor cells (defined as CD45 ^dimCD34 ⁺VEGFR2 ⁺7AAD ^- cells) were measured by flow-cytometry in 71 and 58 patients included in phase 1 trials testing novel anti-vascular or anti-angiogenic agents. Correlations between levels of CECs, circulating VEGFR2 ⁺-BMD progenitor cells, clinical and biological prognostic factors (i.e. the Royal Marsden Hospital (RMH) score), and overall survival (OS) were studied. The median value of CECs was 12 CEC/ml (range 0-154/ml). The median level of VEGFR2 ⁺-BMD progenitor cells was 1.3% (range 0-32.5%) of circulating BMD-CD34 ⁺ progenitors. While OS was not correlated with CEC levels, it was significantly worse in patients with high VEGFR2 ⁺-BMD progenitor levels (>1%) (median OS 9.0 versus 17.0 months), and with a RMH prognostic score >0 (median OS 9.0 versus 24.2 months). The prognostic value of VEGFR2 ⁺-BMD progenitor levels remained significant (hazard ratio (HR) = 2.3, 95% confidence interval (CI), 1.1-4.6, p = 0.02) after multivariate analysis. A composite VEGFR2 ⁺-BMD progenitor level/RHM score ≥2 was significantly associated with an increased risk of death compared to scores of 0 or 1 (median OS 9.0 versus 18.4 months, HR = 2.6 (95% CI, 1.2-5.8, p = 0.02)). High circulating VEGFR2 ⁺-BMD progenitor levels are associated with poor prognostics and when combined to classical clinical and biological parameters could provide a new tool for patient selection in early anticancer drug trials.