Elevated absolute NK cell counts in peripheral blood predict good prognosis in chronic lymphocytic leukemia

The aim of this study was to investigate the prognostic significance of the absolute natural killer (NK) cell counts in peripheral blood in patients with chronic lymphocytic leukemia (CLL). A total of 273 previously untreated patients with CLL from April 2004 and October 2015 were enrolled into this retrospective study. We analysed the T cell subsets of all patients and figured out the number of NK cells. Comparisons of NK cell count as continuous parameter in different groups were described using Mann–Whitney U test and the Kruskal–Wallis test. Kaplan–Meier method was used to survival analysis, and the Cox proportional hazards models were used for the estimation of prognostic factors. NK cell counts were calculated in 273 therapy-naive CLL patients, and higher number of NK cell was observed in those with Binet stage A/B, ZAP-70 < 20%, normal serum albumin and β2-microglobulin levels. Using a NK cell count cut-off of 0.40 × 109/L, patients with lower NK cell count (< 0.40 × 109/L) had a significantly shorter overall survival (OS) than those with higher NK cell count (≥ 0.40 × 109/L) (P = 0.0014). Multivariate analysis showed that NK cell counts remained its prognostic value. However, the effect of NK cell count on time to treatment was not significant. Our results suggest that NK cell count is an independent prognostic marker for OS in patients with CLL and NK cell counts ≥ 0.40 × 109/L can routinely be used to identify patients with favorable survival.