Elevated Serum Thymidine Kinase Levels Identify a Subgroup at High Risk of Disease Progression in Early, Nonsmoldering Chronic Lymphocytic Leukemia

Abstract

AbstractChronic lymphocytic leukemia (CLL) shows a remarkably heterogeneous clinical outcome; survival ranges from several months in advanced stages to more than 10 years in early stages. The Binet and Rai staging systems distinguish three major prognostic subgroups, but do not accurately predict the individual risk of disease progression in early CLL (Binet stage A or Rai stage 0 to II). Because most newly diagnosed CLL patients present with early disease, it seems desirable to search for additional prognostic factors to identify early CLL patients at high risk of rapid progression. It has been shown that elevated serum thymidine kinase (s-TK) levels predict disease progression in CLL. Therefore, this study aimed to assess the prognostic value of s-TK in 122 previously untreated patients with Binet stage A CLL (mean age ± SD, 58.7 ± 8.5 years). In univariate analyses, 18 of the 22 parameters investigated predicted progression-free survival (PFS). In a stepwise multiple regression analysis, only three parameters provided independent prognostic information on PFS: s-TK greater than 7.1 U/L; presence of lymphadenopathy; and white blood cell (WBC) count greater than 75,000/μL. When added to the classification of smoldering versus nonsmoldering CLL, s-TK levels separated two groups within the group of nonsmoldering stage A patients: patients with s-TK values greater than 7.1 U/L had a median PFS of 8 months, whereas patients with s-TK values ≤ 7.1 U/L expected a much longer PFS (49 months; P < .001), similar to smoldering CLL (42 months). The results demonstrate that s-TK is a prognostic parameter that adds independent prognostic information to the definitions of smoldering and nonsmoldering CLL in Binet stage A.