Objective: To assess the prognostic value of serum thymidine kinase (sTK) activity in patients with the myelodysplastic syndrome (MDS).
Patients and methods: The study included 255 patients (144 men, 111 women, median age 67 [14-97] years) in whom primary MDS had been diagnosed between 1986 and 1995 (refractory anaemia [RA]: n = 40; RA with ring sideroblasts: n = 38; RA with increased blasts: n = 76; RA with increased blasts in transformation: n = 45; chronic myelomonocytic leukaemia: n = 56). 69 healthy persons (28 men, 41 women, median age 33 [24-62] years) served as controls. The normal laboratory range for sTK was between 0.9 and 4.9 U/microliter.
Results: At time of diagnosis 83% of patients had sTK levels higher than 5 U/microliter. There was no relationship between sTK levels and the proportion of medullary blasts. But serum sTK levels correlated with LDH activity (P < 0.0005) and with peripheral leukocyte count (P = 0.003). At all times patients with sTK levels < 10 U/microliter had a higher survival rate than those > or = 10 U/microliter. Cumulative survival rates in both groups was 69 +/- 10% (< 10 U/microliter) and 43 +/- 11% (> or = 10 U/microliter), respectively, after 2 years and 37 +/- 9% (< 10 U/microliter) and 20 +/- 7% (> or = 10 U/microliter) after 5 years (P = 0.0002). Multivariate analysis showed that sTK, haemoglobin concentration and proportion of medullary blasts were independent prognostic survival factors.
Conclusions: Most patients with MDS have an increased sTK level when the diagnosis is made. This reflects the impaired proliferation and differentiation of haematopoiesis. sTK is a simply and rapidly measured prognostic indicator for estimating survival probability of patients with MDS.