Serum BAFF (B-CELL Activating Factor Of The TNF Family) predicts time to First Treatment in Early B-CELL Chronic Lymphocytic Leukemia

We analyzed the correlation between well-established biological parameters of prognostic relevance in B-cell chronic lymphocytic leukemia [CLL] (i.e, mutational status of the immunoglobulin heavy chain variable region [IgV_H], ZAP-70− and CD38− expression) and serum levels of BAFF (B-cell activating factor of the TNF family) by evaluating the impact of these variables on the time to first treatment [TFT] in a series of 125 previously untreated Binet stage A B-cell CLL patients. By using a commercial ELISA (R & D Systems, USA) we found that higher levels of BAFF characterized more frequently females (P=0.01), patients with Rai stage 0 (P=0.03), mutated IgV_H disease (P=0.008) and low ZAP-70 expression (P=0.04). In contrast, age (P=0.35), peripheral blood lymphocytosis (PBL)(P=0.09), hemoglobin (Hb) level (P=0.64), platelet (PLT) count (P=0.12), serum β₂-m (P=0.49), LDH (P=0.85) and percentage of CD38-positive B-CLL cells (P=0.63) did not reflect circulating levels of BAFF. We used an optimal cut-point search to determine how to best split soluble BAFF data. Maximally selected log-rank statistics plots identified a BAFF serum concentration of 311 ng/mL as the best cut-off (P<0.0001). Accordingly, patients who had BAFF levels higher than 311 ng/mL experienced a longer TFT (median 108 months) in comparison to patients whose BAFF levels were lower than 311 ng/mL (median 30 months; P<0.0001). Along with serum concentration of BAFF, the univariate Cox proportional hazard model identified Rai substage I–II (P=0.003), lower PLT count (P=0.04), higher PBL count (P=0.01), increased LDH (P=0.01), ZAP-70 expression > 20% (P=0.02) and absence of mutation of IgV_H (P<0.0001) as predictor of shorter TFT. In multivariate analysis only soluble BAFF (Hazard ratio [HR], 6.13; CI 95%, 2.31–16.25) and mutational status of IgV_H, (HR= 2.99; CI 95% 1.33–6.76, P=0.008) maintained their discriminating power. The effects of BAFF on TFT were masked by mutational status of IgV_H in patients with unmutated IgV_H. However, serum levels of BAFF and mutational status of IgV_H had a joint effect on TFT in patients with mutated IgV_H which translates into a segregation of patients with mutated IgV_H in two groups with different TFT according to BAFF levels (HR= 8.9; P<0.0001). Our results indicate that in early B-cell CLL biological profile including among other parameters soluble BAFF may provide a useful insight into the complex interrelationship of prognostic variables. Furthermore, BAFF along with mutational status of IgV_H can be adequately used to predict clinical behaviour of patients with low biological risk.