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.