Deoxythymidine-kinase in cerebrospinal fluid: a new potential "marker" for brain tumours.

A recently developed method for deoxythymidine kinase (dTK) determination was applied to cerebrospinal fluid (CSF) and serum samples, derived from "healthy" individuals and from patients with non-neoplastic or neoplastic disorders of the brain. No dTK activity could be detected in the CSF of healthy individuals or in patients with hydrocephalus or cranio-cerebral trauma. dTK levels ranging from detectable to high were found in the CSF of patients with malignant primary brain tumours or secondary brain tumours, while in some cases of low grade primary brain tumours dTK could not be detected in the CSF. CSF samples taken before and after treatment were available both in some patients with CNS involvement of malignant lymphomas and in some with primary brain tumours. The dTK activity rapidly declined after chemotherapy intrathecally and irradiation, as well as after surgery. Enhanced CSF dTK was not only a feature of malignant CNS processes, but was also found in patients with cerebral haemorrhage penetrating into the CSF. The origin of dTK in CSF and the practical use of quantifying it is discussed.