Use of circulating pregnancy-specific beta 1 glycoprotein as a marker in carcinoma of the breast in women.

Pregnancy-specific beta 1 glycoprotein (SP1) was determined by radioimmunoassay in sera from 27 normal women, 33 women with benign breast disease, and 191 women with carcinoma of the breast, staged for extent of the disease. All diagnostic groups exhibited substantial overlap in SP1 values. Those with benign breast diseases tended to have values at least as high as those with cancer. Normal patients tended to have slightly lower values, but this difference may well have been due to the younger ages of the normal patients in our sample, because SP1 values tended to increase with age. Immunochemical dilutions of SP1 in the serum with the highest value (10.2 ng/ml) did not differ significantly from standard placental SP1.