Serum thymidine kinase 1 correlates to clinical stages and clinical reactions and monitors the outcome of therapy of 1,247 cancer patients in routine clinical settings

Background Thymidine kinase 1 in serum (STK1) has been found to be a reliable proliferation marker in clinical trials. In this study, we examined the significance of STK1 in routine clinical settings. Methods The concentration of STK1 was determined by a sensitive dot blot ECL assay. The STK1 value was correlated to clinical stage and reactions and used for monitoring the outcome of surgery and/or multidrug chemotherapy of 1,247 patients with five different types of carcinomas (lung, esophagus, gastric, head and neck, and thyroid) in routine clinical settings. Results The STK1 values correlated with the clinical stage in patients with lung, esophagus, thyroid, and gastric carcinomas. After treatment, STK1 declined in all tumor groups after treatments (P < 0.01). The STK1 was low (< 2 pM) or decreasing during treatment in patients with clinical reactions of complete response (CR) or partial response (PR), but high (> 2 pM) or increasing in patients with stable disease (SD) or progressive disease (PD), some of them showing metastasis. STK1 also reflected the differences in clinical reactions when surgery and chemotherapy were compared. Conclusion We concluded that the concentration of TK1 in serum correlates to clinical stages and clinical reactions and monitors the effect of tumor therapies, not only in controlled clinical trials, but also in routine clinical settings.