Thymidine kinase 1 in serum predicts increased risk of distant or loco-regional recurrence following surgery in patients with early breast cancer.

The prognostic value of the concentration of serum thymidine kinase 1 (S-TK1) with regard to recurrence in low risk breast cancer patients, 3 months after surgery was evaluated. The concentration of S-TK1 in serum was determined in 120 breast cancer patients at the time of surgery and in 67 patients 3 months after surgery, by anti-TK1 chicken IgY antibody, using a dot-blot immuno-assay. The S-TK1 concentration was compared with the serological activity of thymidine kinase (STK) and of carbohydrate antigen (CA 15-3). A statistically significant trend (unadjusted) was found for recurrence (distant or loco-regional) in patients with a higher S-TK1 concentration, as compared with patients with a lower S-TK1 concentration. A multivariate analysis gave the same results. The hazard rate ratio for developing distant and/or loco-regional recurrence in patients with a higher S-TK1 concentration was about six to seven times higher than in patients with a lower S-TK1 concentration. Our results indicate that the S-TK1 concentration is higher in patients developing distant and/or loco-regional recurrence 3 months post-surgery.