Creatine kinase-BB in the cerebrospinal fluid as a marker of CNS metastases and leptomeningeal carcinomatosis in patients with breast cancer.

To determine whether creatine kinase-BB isoenzyme would be useful in detecting central nervous system metastases secondary to breast cancer, we measured the cerebrospinal fluid (CSF) activity of creatine kinase (CK) and its BB isoenzyme (CK-BB) in 65 consecutive patients suspected of having CNS involvement. All patients underwent neurological evaluation, computer tomography (CT) scan and/or radionuclide scintigraphy and lumbar puncture with CSF examination. Thirty patients had CNS metastases, of whom 18 had parenchymal brain metastases (MET). Twelve had leptomeningeal carcinomatosis (MC), of whom four also had parenchymal brain metastases. Thirty-four patients were concluded not to have CNS involvement, whereas one was considered equivocal. CK-BB activity was significantly higher in patients with CNS metastases than in those without (P less than 0.05). This difference was primarily related to the fact that patients with MC had a significantly higher CK-BB activity than patients without CNS metastases or patients with parenchymal brain metastases only (P less than 0.01 and P less than 0.05, respectively). Taking 0.20 U/l as a tentative cut-off value (the upper limit range of patients without CNS metastases being 0.19 U/l), 10 out of 12 patients with MC had activities above this level. The sensitivity and specificity for having MC were 83% and 87%, and the positive and negative predictive values 60% and 96%, respectively. The sensitivity and negative predictive value for having any CNS metastases were 57% and 72%. Specificity and positive predictive value: 100%. The CSF activity of CK-BB appears to be a contribution in the diagnosis of MC secondary to breast cancer and seems superior to protein and LDH.