Serum creatine kinase isoenzymes in patients with advanced malignant disease

Serum creatine kinase (CK) B subunit (CK-B) activity, as estimated by the enzymatic anti-M immunoinhibition method, and the CK isoenzyme pattern after agarose gel electrophoresis, were studied in 28 patients with advanced, untreated malignant disease. CK-B was above the decision limit, i.e. the discrimination limit used in the diagnosis of acute myocardial infarction (AMI), in 14 patients (50%). Electrophoresis demonstrated, besides CK-MM, an atypical, cathodically migrating CK band in 10 of these patients. This band may represent mitochondrial CK. The CK-BB isoenzyme was detected in 9 and CK-MB in 3 subjects. Histopathologic findings indicated that the occurrence of these isoenzymes was related to tumour burden and the overall severity of the disease. Survival among patients with CK-B elevation was shorter than among other patients. The present findings are relevant to the enzyme diagnosis of AMI and of potential significance for the evaluation of patients with known or suspected malignant tumours.