Significance of Serum Free Light Chains in Chronic Lymphocytic Leukemia (cll) Prognosis

Symptomatic CLL patients need treatment immediately. For these patients, molecular-genetic factors (mutated-unmutated, ZAP 70, ATM, p53) are important prognostic factors of response and survival. Nevertheless, 2/3 of newly diagnosed patients are asymptomatic and require only of follow up that can last for months or years. For these patients overall survival (OS) depends on the time to first treatment (TFT). The most frequent paraprotein produced in CLL is serum free light chain in 50% of the patients. It has recently been shown that serum free light chains (sFLC) and their sum above 60 (κ+λ above 60) are useful prognostic factors for TFT. We therefore studied the eventual prognostic implication of sFLC and the summated FLC-kappa plus FLC-lambda in a CLL patients' series.

143 CLL patients were studied of which 18 needed immediate treatment while 37 more needed treatment during their follow up. 64% and 72%, 28% and 18%, 7.5% and 10%, were in stage 0 and A, 1 and β, 2 and C according to Rai and Binet respectively. Median patients' follow up was 32 months (range 4–228). Light chain restriction was established by flow cytometry or bone marrow biopsy immunohistochemistry. Serum free light chain values were retrospectively determined by nephelometry (Freelite™, the Binding Site Birmingham, UK) in frozen sera drawn at diagnosis. Elevated sFLC values were defined using as cut-off values the 95^th percentile range of healthy individuals. Statistical analysis was performed using SPSS v15.0. Hazard ratios and prognostic significance of abnormal sFLC, HLC and ratios were determined by univariate Cox regression analysis. Kaplan Meier method was used for pictorial representation of survival and time to treatment.

Increased sFLC were found in 45% of the patients while the summated FLC-kappa plus FLC-lambda was higher than 60 mg/dl in 14%. Increased sFLC values as well as values of FLC κ+λ>60 were related to shorter TFT (p=0,0005 and p=0,000003 respectively). In addition, high levels of sFLC and FLC κ+λ >60 correlated with β2-microglobulin (r=0.2, p=0.009 και r=0.2, p=0.03 respectively), serum albumin (r=0.2, p=0.009 only for FLC κ+λ > 60), negatively with hemoglobin (r=-0.3, p=0.000003 και r=-0.2, p=0.0002 respectively), increased LDH (p=0.037 και 0.001 respectively), Rai stage (p=0.03 και 0.003 respectively) and Binet stage (p=0.02 only for FLC κ+λ > 60) and with the presence of beta-symptoms (p=0.004 only for FLC κ+λ > 60). Finally, increased sFLC and FLC κ+λ>60 values correlated with shorter OS (p=0.05 and p=0.003 respectively).

The results of our study confirmed the significance of sFLC in CLL with regard to TFT and their relationship with adverse prognostic clinical and laboratory parameters but also demonstrated for the first time their impact on OS.

No relevant conflicts of interest to declare.