Usefulness of Serum Thymidine Kinase 1 as a Biomarker for Aggressive Clinical Behavior in B-cell Lymphoma

ABSTRACT

BACKGROUND: The cell cycle-dependent enzyme thymidine kinase 1 (TK1) is known to increase during cancer cell proliferation and has been reported as a prognostic marker for various hematologic malignancies and solid tumors. This study aimed to determine the reference interval in Korean healthy controls and to evaluate the usefulness of TK1 as a biomarker for aggressive clinical behavior in B-cell lymphoma patients. METHODS: We enrolled 72 previously untreated patients with B-cell lymphoma and 143 healthy controls. Serum TK1 levels were measured by chemiluminescence immunoassay (Liaison(R), DiaSorin, USA). We established the reference intervals in healthy controls. The diagnostic performance of serum TK1 was studied using receiver operating characteristic (ROC) analysis, and the correlation between the cutoff level for serum TK1 and clinical characteristics of B-cell lymphoma was evaluated. RESULTS: The reference range (95th percentile) of serum TK1 in healthy controls was 5.4-21.8 U/L. There was a clear difference in TK1 levels between patients with B-cell lymphoma and healthy controls (40.6+/-68.5 vs. 11.8+/-4.4 U/L, P or =15.2 U/L) correlated with the advanced clinical stage (P<0.001), bone marrow involvement (P=0.013), international prognostic index score (P=0.001), lactate dehydrogenase level (P=0.001), low Hb level (<12 g/dL) (P=0.028), and lymphocyte count (P=0.023). CONCLUSIONS: The serum TK1 level could serve as a useful biomarker for aggressive clinical behavior in B-cell lymphoma patients.