Prognostic relevance of serum thymidine kinase in primary myelodysplastic syndromes: relationship to development of acute myeloid leukaemia

The aim of this study was to evaluate the possible prognostic relevance of thymidine kinase serum levels (s-TK), an indirect marker of proliferative activity, in myelodysplastic syndromes (MDS). S-TK levels were monitored by means of a radioenzyme assay in 90 patients affected by MDS (22 refractory anaemia, RA; 17 RA with ring sideroblasts, RARS; 21 RA with blast excess, RAEB; 15 RAEB in transformation, RAEB-T; 15 chronic myelomono-cytic leukaemia, CMMoL). Mean s-TK levels (U//tl) measured at diagnosis were 11–9 –12–6 for RA, 11–4–13'6 for RARS, 19–9 – 28–4 for RAEB, 39–6 – 34–3 for RAEB-T and 77–7 – 69–7 for CMMoL (normal values <5U//LI1). With the only exception of a weak relationship with lactate dehydrogenase, no correlation was found between initial s-TK values and other clinical or laboratory parameters, such as age, haemoglobin, white blood cell or platelet count, percentage of bone marrow blasts. MDS patients with s-TK >38 V/fA , a cut-off level selected by means of ROC statistical analysis, showed a significantly shorter survival than those with s-TK <38U//xl (8–2 v 37–4 months, respectively; P < 0–0001). In particular, transformation in acute myeloid leukaemia (AML) occurred in 17/21 (81%) of patients with s-TK >38U//d and 9/69 (13%) of those with lower levels at diagnosis (P < 00001), independently of FAB subtype. High s-TK levels were also useful to predict evolution in AML during the course of the disease in patients with normal initial values. Multivariate analysis confirmed the independent prognostic value of s-TK on both overall survival and risk of acute transformation. We conclude that s-TK may be an important prognostic factor in MDS, strongly correlated with development of AML.