Abstract
New biological prognostic factors have been developed over the last years with the aim of predicting at presentation the heterogeneous clinical course of B chronic lymphocytic leukaemia (B-CLL) and of planning a risk-adapted treatment strategy. Among them ZAP-70 expression on leukemic cells as evaluated by molecular analysis or flow cytometry, initially proposed as surrogate of IgVH mutational status, appears a strong prognostic marker in B-CLL. However the optimal methodological approach to immunophenotipical demonstration of ZAP-70 expression as still matter of debate. We evaluated the cytoplasmic expression of ZAP-70 protein in leukemic cells by immunohistochemical method on bone marrow trephine biopsies taken at diagnosis of 84 patients with B-CLL. We used a mouse anti-human monoclonal antibody to ZAP-70 (clone 2F3.2, 1/200, Upstate, Lake Placid NY) with a polymeric labelling two-step method (Dako cytomation EnVision+, HRP). The results were correlated with age, sex, Binet stage, pattern of bone marrow infiltration, survival and clinical outcome. They were 54 males (64%), aged 34 to 80 years (median 62.5). At presentation 69 (82%) were Binet stage A, 9 (11%) stage B and 6 (7%) stage C. Among the 60 survivors, the median follow-up period from diagnosis was 78.5 months (range 22 – 236 months) Thirty-nine cases (46%) of B-CLL patients had cytoplasmic expression of ZAP-70. This group of patients presented higher percentage of advanced Binet stage (B–C) (p= 0.001). The ZAP-70 positivity was significantly related to inferior OS (55% vs 90% at 7 years)(HR 4.67 CI 1.95–11.14) and PFS (15% vs 57% at 7 years) (HR 5.52 CI 2.57–11.86), confirmed in multivariate analysis. ZAP-70 expression was correlated to poorer outcome also when we evaluated only the 69 stage A patients and the 56 cases with non-diffuse bone marrow infiltration, whereas in patients with diffuse pattern ZAP-70 expression had no prognostic significance. In conclusion, immunohistological detection of ZAP-70 on bone marrow samples at diagnosis appears a useful methodological approach to identify patients with different prognosis in B-CLL.
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