The investigation of lactalbumin as a possible marker for human breast cancer

Measurable amounts of the whey protein lactalbumin have been found in the cytosol of over a third of 89 primary breast carcinomas using a specific radioimmunoassay. With a modification of the method which prevents interference from endogenous antibodies, serum levels of lactalbumin have been measured in 83 subjects with breast cancer, 45 subjects with benign mammary dysplasic and 63 controls. In earlier studies of normal women, we found that circulating lactalbumin was not found in subjects aged over 45 yr but was commonly present below that age. Since the patients with benign dysplasia had a mean age of 35.0 yr and the breast carcinoma patients a mean age of 60.4 yr, separate control groups were necessary for the two patient groups. Circulating lactalbumin was found in 12% of patients with operable breast cancer, 24% of patients with metastatic disease and in none of the age-matched controls. Circulating lactalbumin was detected no more often in the patients with benign dysplasia than in corresponding controls. It appears that a sizeable minority of human breast carcinomas are able to synthesise lactalbumin in sufficient quantity to produce a measurable level in the blood.