The Frequency of Occurrence of Minimal Residual Disease into Different Prognostic Groups of Patients with Chronic Lymphocytic Leukemia

Background. It is known, that genetic factors and the absence of minimal residual disease (MRD) are strongly affecting prognosis of chronic lymphocytic leukemia (CLL).

Aim. To determine the influence of genetic abnormalities (GA) on achieving MRD-negative remissions in patients with CLL.

Methods. Twenty-four adult pts (median age 57 years, range 35-67; male 14, female 10) with newly diagnosed CLL were included. The CLL was diagnosed according to the standard basic examination (complete blood count with differential, multicolor flow cytometry (MFC) of blood and bone marrow (BM), lymph node and BM immunohistochemistry (IHC), computered tomography). Cytogenetic studies were performed on blood samples using standard GTG-method. Interphase FISH analyses were performed according to the manufacturer's protocol using DNA probes: LSI 13(RB1)13q14, LSI ATM (11q22), CEP12, LSI TP53 (17p13.1) (Abbott). Immunophenotype (IFT) of CLL cells assessed with combinations: CD3/CD19, CD19/CD5, CD19/CD11c, CD19/CD20, CD19/CD22, CD19/CD23, CD19/CD25, CD19/CD38, CD19/CD43, CD19/CD81, CD19/HLA-DR, and CD19/CD5/CD23. We have used NCI revised guidelines (Hallek M, et al., 2008) for treatment initiation and assessment of response after completion of primary therapy with rituximab-based regimens (FCR or RB). All patients treated subsequently with rituximab maintenance. MRD was detected by MFC.

Results. The frequency of GA in CLL was 50.0% (12/24): 15.0% (3/20) - by conventional karyotyping, 47.8% (11/23) - by FISH analyses and 9.5% (2/21) - using both methods. Stratification of patients into prognostic groups based on identified GA. Favorable prognosis (Group 1) - patients with del(13q) (n = 5); neutral prognosis (Group 2) - normal karyotype (n = 12) or trisomy of chromosome 12 (n = 3); unfavorable prognosis (Group 3) - del(11q) (n = 3) or the complex karyotype (n = 1).

Statistically significant differences in the frequency of achieving MRD-negative remissions between FCR (5/11) vs. RB (5/13) were not detected (p<0.05).

Complete remissions (CR) were reached in 37.5% (9/24) pts, partial remissions (PR) - 62.5% (15/24). The MRD-negative remissions were reached in 10 patients: in Group 1 - 2/5 (40%; CR - 1), in Group 2 - 5/15 (33.3%, CR - 6), in Group 3 - 75.0% (3/4; CR - 2).

Statistically significant differences in PFS were detected between MRD-negative vs. MRD-positive groups (p=0.03). Median PFS in MRD-negative has not been reached. Median PFS MRD-positive was 33.1 month.

Conclusions. Further researches aimed at examining the relationship between the presence or absence of MRD and genetic prognostic groups, will help to understand the most important factors affecting the overall and progression-free survival.