Serum soluble CD23 levels are an independent predictor of time to first treatment in chronic lymphocytic leukemia.

Serum soluble CD23 (sCD23) levels have been acknowledged as a prognostic factor in patients with chronic lymphocytic leukemia (CLL), but their potential relevance has not been analyzed in recent times. We retrospectively studied 338 CLL, small lymphocytic lymphoma, or CLL-type monoclonal B-cell lymphocytosis patients from a single institution, with available sCD23 levels at diagnosis. Baseline features and outcomes were compared between patients with sCD23 ≤/>1000 UI/L. The 140 patients (41%) who had sCD23 > 1000 UI/L showed adverse-risk clinical and biological characteristics. High sCD23 levels were predictive of a shorter time to first treatment (5-year probability of requiring treatment: 60 vs. 20%, p < 0.0001; hazard ratio (HR) = 1.72, p = 0.003 in a multivariable model also including the CLL International Prognostic Index and the absolute lymphocyte count), and a poorer 5-year overall survival (70 vs. 82%, p = 0.0009). These data suggest the potential of sCD23 to predict treatment-free survival and to shed light on mechanisms of activity and resistance to CD23-directed therapies.