gamma-Glutamyl transferase and breast cancer risk.

These results suggest that premenopausal women with high normal (above median) serum GGT or elevated levels (< or =40 IU l(-1)) are at increased risk of breast cancer and might benefit from close surveillance, possibly with breast magnetic resonance imaging scans. Serum GGT may mark previous exposure to carcinogens and lead to the identification of DNA adducts involved in mammary carcinogenesis.