Elevated serum levels of creatine kinase BB in breast cancer.

Creatine kinase BB serum levels were evaluated by radioimmunoassay in patients with benign or malignant breast pathology. Elevated enzyme levels were observed in 6 out of 20 (30%) patients with primary breast cancer. After surgery the levels fell to normal values only in patients without nodal involvement. Six out of 28 (21%) patients with benign breast lesions and 4 out of 38 (13%) patients with metastatic breast cancer also showed increased levels of the enzyme. Most of the patients with high creatine kinase BB serum levels were found to have estrogen and progesterone receptor-positive tumors. These findings suggest that creatine kinase BB can barely be considered a marker of malignancy in breast pathology, but rather an indicator of hormone dependency in breast cancer.