Serum human alpha-lactalbumin as a marker for breast cancer.

Serum levels of alpha-lactalbumin were assayed using a monoclonal antibody specific for this breast specific molecule. Elevated levels were found in 87% (48/55) of sera from women in the third trimester of pregnancy (29.1 +/- 7.4 ng ml-1), from 64% (62/97) of patients with breast cancer (23.4 +/- 5.6 ng ml-1), and from 70% (56/80) of patients with gynaecological cancers (19.4 +/- 6.7 ng ml-1). These alpha-lactalbumin levels were significantly higher (P less than 0.001) than those for men and non-pregnant women (11.0 +/- 2.3 ng ml-1) and for patients with other, non-gynaecological cancers (13.4 +/- 3.6 ng ml-1). The alpha-lactalbumin levels were higher in patients with stage IV breast cancer than those with stage I-III breast cancer. The overall sensitivity and specificity of the radioimmunoassay were 72% and 75% respectively. These findings suggest that the assessment of serum levels of alpha-lactalbumin may be useful as a marker for monitoring breast cancer.