Significance of pregnancy-associated alpha 2-glycoprotein (alpha 2-PAG) in patients with breast, gastric and colorectal cancer.

Pregnancy-associated alpha 2-glycoprotein (alpha 2-PAG) levels were measured in human sera by a modification of Laurell's electroimmunoassay using rabbit anti-alpha 2-PAG serum. Sera were obtained from healthy controls (32 males and 46 females), patients with benign breast diseases (55 cases), and patients with breast (82 cases), gastric (89 cases), or colorectal (22 cases) cancers. In healthy controls, the mean alpha 2-PAG value for females was higher than that for males (p less than 0.05), so alpha 2-PAG values for males and females were considered separately in this study. Serum alpha 2-PAG levels in patients with benign breast tumors were almost the same as those of controls. In patients with primary breast and gastric cancer, alpha 2-PAG levels were higher than those of controls (p less than 0.005) and tended to increase with progress of the disease. Raised alpha 2-PAG levels decreased in these patients after curative surgery. These results show that serum alpha 2-PAG is useful as a marker in both the initial diagnosis and follow-up of breast and gastric cancer. The reliability of alpha 2-PAG as a tumor-associated marker was reinforced by comparison of the positive rates of the three parameters alpha 2-PAG, carcinoembryonic antigen (CEA), and immunosuppressive acidic protein (IAP) in patients with breast and gastric cancer.