Serum thymidine kinase in colorectal neoplasia

Thymidine kinase (TK), an enzyme known to be associated with DNA synthesis, has been measured in the serum of patients with asymptomatic colorectal adenomas (n = 40), asymptomatic colorectal carcinoma (n = 21) and patients known to have hepatic metastases form colorectal tumours (n = 33); enzyme levels have been compared with an age-matched group of asymptomatic people with no evidence of colorectal neoplasia at screening colonoscopy (n = 26). TK activity in patients with metastatic disease (median 4.23; range 2.03–14.12 pmol/ml/h) and in patients with adenomas (median 2.33; range 1.59–8.73 pmol/ml/h) was significantly higher than in the normal controls (median 2.04; range 1.29–5.40 pmol/ml/h). However TK activity in patients with asymptomatic cancer (median 1.85; range 1.00–4.50 pmol/ml/h) was not significantly different from the control group.