Low Serum Creatine Kinase Levels in Breast Cancer Patients: A Case-Control Study

BACKGROUND Previous studies provide an ambiguous picture of creatine kinase (CK) expression and activities in malignancy. The aim of this study was to investigate the role of serum CK level in breast cancer patients. PATIENTS AND METHODS 823 female patients diagnosed with breast cancer were consecutively recruited as cases, and 823 age-match patients with benign breast disease were selected as controls. Serum CK was analyzed by commercially available standardized methods. RESULTS Serum CK level was significantly associated with breast cancer (P = 0.005) and subtypes of breast cancer, including breast cancer with diameter>2 cm (P = 0.031) and stage IIIbreast cancer (P = 0.025). The mean serum CK level in patients with>2 cm tumor was significantly lower than that in≤2 cm (P = 0.0475), and the mean serum CK level of stage III breast cancer patients was significantly lower than that of stage I and II breast cancer patients (P = 0.0246). Furthermore, a significant difference (P = 0.004) was observed between serum CK level and ERBB2+breast cancer not other molecular subtypes. CONCLUSIONS Serum CK levels in cases was significantly lower compared with controls. Notably, our results indicated for the first time that there was a negative correlation between serum CK levels and breast cancer stage. Serum CK level, which may reflect the status of host immunity, may be an important factor in determining breast cancer development and progression.