MKI67 and neoplasm: Two of the three discordant cases between C1D1 and C1D15 time points had serum TK levels in the 20s (with 20 Du/L being the detection limit) at C1D1 (Fig. 5a and b), and one of the three discordant cases between C1D15 and surgery time points had a minimal change in both tumor Ki-67 and serum TK levels.