Circulating levels of epithelial membrane antigen in patients with breast or colorectal-cancer

Epithelial membrane antigen (EMA) is expressed by adenocarcinomas of the breast, ovary and colon and has been suggested as a circulating tumour marker. Serum EMA levels were measured in 126 patients, 31 with colorectal cancer, 52 with breast cancer and 43 age matched controls using a competitive binding radioimmunoassay and the rat anti-EMA monoclonal antibody (MAb) ICR2. The EMA levels in the control group varied widely from 90-3240ng/ml with a median value of 570ng/ml. This was not significantly different from the levels in patients with colorectal cancer (60-8530, median 580ng/ml) or those with breast cancer (210-13300, median 655ng/ml). However, the highest EMA levels (>5000ng/ml) were found in patients with cancer. The wide range of EMA levels in the control group prohibit its use for screening.