Serum Thymidine Kinase 1 Activity in Solid Tumor (Breast and Colorectal Cancer) Patients Treated With Adjuvant Chemotherapy

BACKGROUND: The aim of this study was to evaluate the changing of TK1 (where TK is thymidine kinase) activity before and after adjuvant chemotherapy in patients with breast and colorectal cancer. METHODS: The study included 16 breast cancer, 25 colorectal cancer, and 38 healthy volunteers as the control group. Blood samples were taken twice from each patient; first at the beginning of the chemotherapy and second after six cycles of chemotherapy. TK1 activity was measured enzyme immunoassay method. RESULTS: The mean TK1 activity in the breast and colorectal cancer was significantly higher than the controls. TK1 activity in the colorectal cancer was higher than the breast cancer but this difference was not significant. TK1 activity after six doses of chemotherapy was lower than baseline TK1 activity before the start of chemotherapy in breast and colorectal cancer. TK1 activity was positively correlated with CA15-3, before and after chemotherapy in patients with breast cancer. TK1 activity in the colorectal cancer was also positively correlated with CA19-9, before and after chemotherapy. The values for the cutoff point, sensitivity, specificity, and the area under curve were determined for TK1 as >44.36 Du/L, 68.29%, 100% and 0.819, respectively in all subjects. CONCLUSION: Our results showed that serum TK1 activity in patients with breast and colorectal cancer was significantly higher than that of the healthy controls. Moreover, after the completion of chemotherapy the values were lower than baseline. Pretreatment TK1 activity should be considered as a useful marker for assessment tumor cell proliferation in breast and colorectal cancer. Further work is needed to understand TK1 activity better in large populations of patients with solid tumor.