7-ethoxyresorufin O-deethylase (EROD) activity is not capable of reflecting the overall malignant potential of breast cancer tissue.

7-Ethoxylesorufin O-deethylase (EROD) (mainly catalyzed by cytochrome P450 (CYP) 1A1 and used as a marker for CYP 1A1) activity was measured in the breast tumor and surrounding tumor free (normal) tissues of 37 female breast cancer patients with infiltrating ductal carcinoma. About 11% of the tumor and normal breast tissue samples lacked the enzyme activity. Large interindividual variations in the activities of EROD were found in both tumor and normal tissues ranging from 0 to 283 and 0 to 801 fmol/mg/min, respectively. However, no significant difference was noted between the mean EROD activities of tumor and normal breast tissues. This tendency did not change with the stage and grade of the malignancy and menopausal status. No significant correlation was observed between the EROD activity and stage or grade of malignancy (p > 0.05). Thus, it appears that EROD activity is not capable of reflecting the overall malignant potential of breast cancer tissue.