Serum β2-Microglobulin and Serum Thymidine Kinase are Independent Predictors of Progression-Free Survival in Chronic Lymphocytic Leukemia and Immunocytoma

Abstract

Chronic lymphocytic leukemia (CLL) and immunocytoma (IC) are remarkably heterogeneous with regard to their clinical course. The current staging systems can distinguish prognostic subgroups, but do not seem to predict the risk of disease progression of an individual patient with sufficient accuracy. Given the increase of treatment options for CLL and IC, additional parameters are needed to decide which patients may benefit from early or intensified treatment. It has been shown that two biochemical markers, serum beta 2-microglobulin (s-beta 2M) and serum thymidine kinase (s-TK), might identify CLL and IC patients at high risk of disease progression. Therefore, the prognostic value of these two serum parameters was compared with a panel of several established prognostic factors in a prospective clinical trial. 113 patients with CLL and 41 patients with IC (mean age +/- SD 63.9 +/- 10.7 years) were included. The following parameters were determined: histopathological diagnosis (IC vs. CLL), age, sex, performance status (Karnofsky index), B symptoms, peripheral blood lymphocyte count, platelet count, blood hemoglobin, serum lactate dehydrogenase (s-LDH), s-beta 2M, s-TK, serum creatinine, number of lymph node areas involved, prior therapy, and the time from diagnosis to inclusion in the study. Univariate analyses showed that nine parameters (Karnofsky index, peripheral blood lymphocytosis, platelet count, blood hemoglobin, lymph node areas involved, pretreatment, s-LDH, s-beta 2M, and s-TK) significantly predicted progression-free survival. In a Cox regression model, only four of these parameters provided independent prognostic information on progression-free survival: 1. s-beta 2M, 2. Karnofsky index, 3. platelet count, and 4. s-TK. The results show that s-beta 2M and s-TK independently predict progression-free survival in patients with CLL and IC, and suggest that these prognostic factors may allow an improved prediction of progression-free survival, particularly in early disease stages.