Elevation of brain-type creatine kinase in serum from patients with carcinoma.

The brain isoenzyme of creatine kinase (CK BB) occurs in trace amounts in normal serum and is moderately increased in only a small number of non-oncological conditions. Although many tissues and tumors contain CK BB, we observed serum elevations only in certain carcinomas. Eleven patients with tissue-proven small cell anaplastic carcinoma (SCAC) of the lung had striking elevations of serum CK BB and no evidence of central nervous system (CNS) metastases. Significant increases were also observed in three cases of prostatic carcinoma with no apparent CNS involvement, and in one case each of adenocarcinoma and SCAC of the lung with proven CNS metastases. Three patients with SCAC of lung without distant metastases, three with SCAC of the esophagus with distant metastases but no known CNS involvement, and 17 patients with oncological conditions other than SCAC of the lung or adenocarcinoma of the prostate have failed to show elevation in serum CK BB activity. Serum CK BB may be useful as a diagnostic marker or indicator of metastases for some carcinomas.