Defining the 10 Year Risk of Disease Progression in Stage A0 CLL.

80% of patients with CLL present with a lymphocytosis detected on a routine blood count. Many studies have identified risk factors for disease progression but there remains uncertainty about the magnitude of risk and which factors are most useful in determining this risk. To address this we have studied a cohort of 122 stage A0 patients who presented with a lymphocytosis and typical CLL immunophenotype before 1996 and whose CLL has either progressed or remained stable over a 10 year period. All patients were reviewed at least annually. Disease progression was defined as the need for anti-leukemic therapy, an increase in stage or a downward trend in haemoglobin or platelet count, progressive lymphadenopathy or splenomegaly or constitutional symptoms. Karyotypic data, from analysis of G banded metaphases derived fromTPA stimulated lymphocyte cultures, were available on all cases at diagnosis. CD38 and ZAP 70 expression were measured on DMSO frozen cells. VH gene usage and mutational status, and telomere length were assessed on frozen DNA samples, while interphase FISH for del 13q14, del 11q and 17p (ATM and p53 loss) and trisomy 12, was undertaken on fixed cell suspensions. All samples had been collected and stored at, or close to the time of diagnosis.

50 patients had progressive disease. Of the 72 patients with stable disease, the lymphocyte count remained below 20x10⁹/l in 53 and rose with a lymphocyte doubling time of > 1 year in the remainding 19 (termed slowly progressive). In univariate analysis, a lymphocyte count of > 20x10⁹/l, unmutated VH genes, high expression of CD38 (cut off 30%) and ZAP70, del 11q, abnormal presenting karyotype and short telomere length all predicted for disease progression. There was no difference in VH gene usage between the progressive and stable groups. Among the 107 patients for whom lymphocyte count, VH gene mutational status, CD38 and ZAP 70 expression are all currently available, the number of poor risk factors in the progressive and stable groups is shown in Table 1. There was no difference in the number of risk factors between the stable and slowly progressive groups. Del 11q was found in 9 progressive cases all of whom had 2 or more risk factors. P53 loss was found in a single patient with stable disease and no risk factors.

20/122 patients presented with a lymphocyte count < 5.0x10⁹/l, below which patients have been considered to have monoclonal B cell lymphocytosis. Interestingly, 5 of these developed progressive disease. Using only the lymphocyte count, CD38 and ZAP 70 expression, Table 2 shows the risk of disease progression according to the risk factors present.

In summary, once ZAP 70 measurement by flow cytometry is standardized, readily available prognostic tests can provide a quantitative estimate of the risk of disease progression. Performing interphase FISH for 11q and p53 loss in poorer risk cases only may provide additional prognostic information.