Serum thymidine kinase in non-Hodgkin lymphomas with special regard to multiple myeloma.

S-TK (Serum thymidine kinase) levels were determined by means of a radioenzyme assay (REA). In 95% of healthy controls (n = 97), S-TK values were below 8.5 U/L. In patients with monoclonal gammopathies of undetermined significance (MGUS) (n = 27) or polyclonal gammopathies (n = 45) the cut off was 10.3 U/L respectively 25 U/L. Patients with viral disease (n = 16), especially infections with Epstein-Barr virus, Hepatitis-virus and HIV, had elevated S-TK values of up to 215 U/L. In 95 patients with multiple myeloma (MM) and 103 patients with other various non-Hodgkin lymphomas (NHL) S-TK levels were investigated. With regard to monoclonal gammopathies, MGUS had lower S-TK than MM patients (p < 0.05) and patients with stage I MM according to Durie and Salmon had S-TK levels significantly lower than those with more advanced stages (p < 0.01). There was a correlation between S-TK and plasma cell labeling index (r = 0.56, p < 0.001). Patients with chronic lymphocytic leukemia showed significantly higher S-TK levels in the RAI stages 3 and 4 than in stages 1 and 2 (p < 0.01). In cases of other malignant NHL in progression sensitivities of S-TK were found to be: immunocytoma 36%, centrocytic/centroblastic-centrocytic lymphoma 54% and high-grade NHL 40% (cut off defined on lymphomas in remission). S-TK levels varied in MM according to the course of disease and response to therapy decreasing at remission and increasing again at relapse. Analogous variations were found in the other NHL. After two years, 83% of patients with a pretreatment S-TK of < 10 U/L and 47% of the patients with a S-TK of > or = 10 U/L were still alive. S-TK proved to be a highly significant prognostic indicator for MM patients (log-rank and Wilcoxon: p < 0.0001). In the other NHL patients with a S-TK level greater than 10 U/L had a median follow-up of only 7 months. NHL patients with lower S-TK levels did not yet reach the median survival time (log-rank and Wilcoxon. p < 0.005). Our results suggest that the determination of S-TK may help to monitor the clinical course of NHL during therapy and predict the prognosis of NHL.