Serum macro creatine kinase type 2 as a tumor marker in lung cancer: comparison with carcinoembryonic antigen

Macro creatine kinase type 2 (MCK-2), an atypical cathodically migrating creatine kinase isoenzyme, was first detected in the serum of a breast cancer patient in 1978. In recent years, MCK-2 was also found in the sera of several malignancies and has been proposed as a potential tumor marker. Forty two patients with lung cancer. The rates of MCK-2 presence in serum were 56.8%, 29.6%, and 0%, respectively, for primary lung cancer, inflammatory lung disease and normal controls. In primary lung cancer, the rate of presence of MCK-2 was higher than CEA (40.0%), and appeared more frequently in epidermoid cancer (71.3%) and in stages 3 and 4 (65.4%). Serial examinations postoperatively showed that MCK-2 became negative after resection. Carcinoembryonic antigen, MCK-2 or a combination of both was evaluated as a diagnostic aid in 37 patients with a peripheral pulmonary nodule. Sensitivity, specificity and accuracy were 32.0%, 90.9%, 50.0%, 36.4%, 93.3%, 59.5%; 43.8%, 90.5%, 70.3%, respectively, for CEA, MCK-2, and CEA plus MCK-2. It is concluded that MCK-2 is comparable to CEA as a tumor marker in lung cancer. The combination of MCK-2 and CEA is of value as a diagnostic aid in patients with a peripheral pulmonary nodule.