Prognostic value of serum markers of established impact on prognosis in relation with ZAP-70 expression in B-CLL patients

A number of serum parameters such as thymidine kinase (TK), beta2microglobulin (B2-MG) and soluble CD23 (sCD23) have been considered prognostic markers in B-cell chronic lymphocytic leukaemia (B-CLL). Aim of this study was to assess the prognostic value of these parameters in our retrospective series of CLL patients in relation with ZAP-70 expression, tested by immunohistochemistry (ICH) in bone mar- row (BM) biopsies. Methods. We measured the levels of TK, B2-MG and sCD23 in the sera, obtained at diagnosis and stored at –20°C, and eval- uated ZAP-70 expression of leukemic cells in BM biopsies of 172 B-CLL patients, selected by the availability of both these samples at diagnosis. They were 107 males (62%) and 65 females, aged 33 to 85 years (medi- an 63). At diagnosis 139 (81%) were Binet stage A, 26 (15%) B and 7 (4%) stage C. The median follow-up period from diagnosis was 63 months (range 6-246 months). Serum levels of TK activity were measured by a commercial radioenzyme assay and sCD23 levels by a commercial ELISA kit. Threshold for TK was considered 9.14 U/L (mean value of 80 healthy adults + 2SD) and for sCD23 was set at value of 60 U/mL (mean of 30 normal samples was 1.24±0.34 U/mL). Raised B2MG value was defined as ≥2.1 mg/L. ZAP-70 expression by leukemic cells was detected in BM biopsies by ICH using a mouse anti- human monoclonal antibody to ZAP-70 (clone 2F3.2, Upstate, Lake Placid, NewYork). Results. Results are reported in the table: all 4 prognos- tic parameters (serum levels of TK >9.14 U/L, sCD23 >60 U/mL, B2-MG ≥2.1 mg/L and ZAP-70 expression) were associated with shorter TTP, but only raised B2-MG and ZAP-70 positivity affected OS. At multivariate analysis only ZAP-70 positivity was associated both with shorter TTP and OS, elevated sCD23 levels with shorter TTP. The association with poorer TTP and OS was confirmed only for ZAP-70 positivity when we limited the analysis to the 139 Binet stage A patients. Median OS and TTP of 54 stage A ZAP-70 positive patients were 143 and 45 months, respectively, vs not reached of 85 stage A ZAP-70 negative. Mutational IgVH gene status was analysed in 62/172 patients (34 mutated and 28 unmutated). Concordance with ZAP-70 expression was found in 84% of cases. Conclusions. Although different serum markers appeared to be of prognostic relevance at univariate analysis, only ZAP-70 expression indipendently influenced survival in our CLL series, and particolarly in Binet stage A patients.