Aim:

Serum thymidine kinase 1 (TK1) is a sensitive marker of tumor cell proliferation.In this study we aimed to investigate the prognostic significance of serum TK1 activity in metastatic colorectal cancer (MCRC) patients receiving palliative chemotherapy.

Materials and Methods:

We prospectively measured serum TK1 activity immediately before the first and second cycle of the treatment in 46 consecutive metastatic MCRC patients. 10 healthy volunteers were also included as a control group. TK1 activity was measured by means of high sensitive non-radioactive DIVITUM assay. The patient's clinical and biochemical parameters, serum CEA and CA 19.9 levels and serum TK1 activity levels relation with survival were analyzed.

Results:

The mean TK1 level in the study group was significantly higher than the controls (162.1± 27.8 vs 32.97±7.307; p<0.03, respectively). In multivariate analysis TK1 levels before chemotherapy and weight loss remained as independent prognostic factors ( p=0.001; 0.018, respectively). Patients with TK1 activity level above 65 Du/L and 230 Du/L had a longer PFS (624 vs. 231 days) and OS time respectively (p <0.0001 for each cut off value).

Conclusion:

In this study we demonstrated that in the setting of MCRC a significant relation between TK1 levels and survival exists. We consider our results a step further for validation of serum TK1 activity level as an independent prognostic factor in metastatic solid organ tumors.

Keywords: Metastatic colorectal cancer, chemotherapy, progression free survival, overall survival, thymidine kinase