Prognostic Value of β2-Microglobulin (β2M) Expression on Lymphocyte Surface in Chronic B-Lymphocytic Leukemia (B-CLL)

Abstract

Background: Modern therapy diminished prognostic significance of serum β2M level.Aims: This study was designed to investigate the correlation between the number of lymphocytes expressing β2M, serum β2M level, and the results of treatment.Methods: 45 patients (pts) were included (Binet stage B, 36 and C, 9). β2M expression on the lymphocyte surface was detected with immunocytochemical method by means of Dako-Cytomation LSAB2 System HRP, β2M serum level by ELISA.Results: In 29 pts β2M was expressed on 80–100% of lymphocytes (group I), in 16 pts on 35–79% (group II). Number of lymphocytes expressing β2M did not correlate with lumphocyte dimension, form of nucleus, and presence of prolymphocytes in peripheral blood (PB). β2M serum level ranged from 3,0 to 10,5 mg/L. Number of leukocytes and lymphocytes in PB and bone marrow in both groups had no difference. Number of pts with normal β2M serum level (3,5 mg/L or less) was practically the same (group I, 13,8%; group II, 18,8%). Among pts with high β2M serum level (> 6 mg/L) there were 28% in group I and 69,0% in group II. Increased level of LDG (>450 MU/L) was detected in 10% of pts of group I and in 50% in group II. Treatment in both groups was similar: regimens with fludarabine–gr.I, 23 of 29 pts and gr.II, 12 of 16; R-COP–gr.I, 3 pts and gr.II, 2 pts. Two pts in gr.II received leukeran; 3 pts in gr.I didn't need any treatment. Of 42 pts treated 20 pts achieved complete remission; 13, partial remission, and 9 pts failed. In gr.I complete remission was achieved in 17 of 26 treated pts (65,4%), in gr.II, in 3 of 16 (18,8%), p=0,0038. Partial remission was received in 6 pts of gr.I (23,1%) and in 7 pts (43,8%) of gr.II, p=0,14. Three pts of gr.I (11,5%) and 6 pts of gr.II (37,2%) failed (p=0,05).Conclusion: Comparison of the therapy results showed that β2M expression on large number (80–100%) of lymphocytes in B-CLL can be considered as the favourable prognostic sign. It was associated with lower level (<6 mg/L) of serum β2M (in 71,2% vs. 31% of pts, p=0,009) and LDG (90% vs. 50% of pts, p=0,0051). Disclosure: No relevant conflicts of interest to declare.