Zap-70 on Bone Marrow Biopsy Is a Good Prognostic Indicator in B-CLL.

Bone marrow biopsies (BMB) taken at the time of diagnosis of 108 patients with chronic lymphocytic leukemia (B-CLL) (median age: 62 years, range: 36–81; M/F ratio: 2/1) were collected between 1985 and 2004, and tested immunohistochemically for the expression of ZAP-70 (zeta-associated protein 70), “Anti-ZAP-70 (human), clone 2F3.2 (mouse monoclonal IgG2a)”. There were degrees of ZAP-70 expression: “negative (a)” (58 patients), “weak (b)” (20 patients) and “intense (c)” (30 patients)” in comparison with natural killer (NK) and T-cell ZAP-70 expression (BMB positive when 20% of B-CLL cells express ZAP-70). The cases were analysed separately by three different experts.

In terms of BMB morphology, proliferative centres were 36% in (a) 35% in (b) and 47% in (c); a diffuse pattern: 8.6% in (a), 10% in (b) and 13% in (c); a nodular pattern: 66% in (a), 55% in (b) and 37% in (c): (a) vs (b+c) (p=0.024), (a+b) vs (c) (p=0.014). The different degrees of ZAP-70 expression correlated with two groups of patients according to the Rai and Binet criteria: “0-I-II, A” and “II-III-IV, B, C”. Cases (a) correspond more frequently to the first, and (b+c) to the second (p=0.013); moreover, cases (a+b) correspond more frequently to the first group, and (c) to the second (p=0.0026).

A lymphocyte doubling time (LDT) of less than six months and less than one year was most frequent in (c) (p=0.00044) (p=0.0065). An LDT of less than one year was more frequent in (b+c) vs (a) (p=0,01). Patients receiving no therapy were more frequent in (a) or (a+b) (p=0.00011) (p=0.00045). Patients receiving no therapy or only one line of treatment were more frequent in (a) or (a+b) (p=3.2x10–5) (p=0.0073). Cytogenetic abnormalities were more frequent in (a) or (a+b) (p=0.017) (p=0.022), and complex caryotypes more frequent in (a+b), (p=0.016). The incidence of death was lower in (a+b) than (c) (8% vs 27%) (p=0.041).

Mann-Whitney analysis showed a statistical difference between (a+b) and (c) for the following variables at diagnosis: PLT (p=0.02); WBC (p=0.05); Ly (p=0.055); LDH (p=0.015); B2m (p=0.0005); splenomegaly (p=0.03); and a statistical difference between (a) vs (b+c) for the following variables at diagnosis: PLT (p=0.044); LDH (p=0.006); B2m (p=0.003); percentage of bone marrow infiltrate (p=0.055); CD 38 flow-cytometry (p=0.0009). Kruskall-Wallis analysis of (a) vs (b) vs (c) showed a statistical difference for the following variables at diagnosis: LDH (p=0.01); B2m (p=0.0017); CD 38 flow-cytometry (p=0.0051). These data confirm the prognostic significance of ZAP-70 expression in patients with B-CLL, and its good correlation with clinical and cytogenetic parameters and the Rai-Binet classification.