Neuron‐specific enolase and thymidine kinase as an aid to the diagnosis and treatment monitoring of small cell lung cancer

Abstract
The serum levels of neuron specific enolase (s-NSE) and thymidine kinase (s-TK) were studied in detail in patients with small cell lung cancer (SCLC) to evaluate as to whether their combined use may aid to diagnosis and follow-up of this particular tumor. Only s-NSE could differentiate between SCLC and non-small cell lung cancer (NSCLC) or benign pulmonary diseases (BPD) to some extent, pathologic serum concentrations occurring in 81%, 17%, and 0%, respectively. The comparable figures for s-TK were 62%, 24%, and 28%, respectively. Serum NSE decreased and increased parallelling tumor regression and progression, respectively, except when brain metastases were present. Alterations of s-TK, in contrast, did not usually mirror the course of disease. During initial chemotherapy (CT) a transitory increase of serum levels was observed for both NSE and TK. Monitoring, based on daily blood samples, showed comparable peaks only for s-TK during the following CT cycles, whereas s-NSE was within the normal range even when tumor mass was still present. Those subsequent s-TK peaks under CT may be due to tumor cell lysis as a result of CT indicating the efficacy of treatment by this way. Rapidly proliferating tissues such as bone marrow or bowel mucosa, have also to be considered as possible sources of s-TK.