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 myelomonocytic leukaemia, CMMoL). Mean s-TK levels (U/μl) 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 38 U/μl, a cut-off level selected by means of ROC statistical analysis, showed a significantly shorter survival than those with s-TK 38 U/μl and 9/69 (13%) of those with lower levels at diagnosis (P <0.0001), 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.