Comparison of circulating MAM-6 and CEA levels and correlation with the estrogen receptor in patients with breast cancer.

MAM-6 and CEA serum levels of 136 staged breast cancer patients were determined concomitantly. The sensitivities of the MAM-6 assay using monoclonal antibody (MAb) 115D8 and a polyclonal CEA assay were equally low and only a limited number of patients with early stages of breast cancer showed elevated antigen levels. However, the sensitivity rose to 75% for MAM-6 and to 60% for CEA in stage-IV patients. The levels of both antigens correlated well in the sera of these patients, although MAM-6 serum levels were elevated more frequently, while only in a few cases were MAM-6-negative sera CEA-positive. A group of stage-II breast cancer patients who eventually developed distant metastases was followed in a longitudinal study. Tumor progression or regression was clinically determined and compared with the MAM-6 and CEA serum levels in order to establish the value of each assay for the monitoring of breast cancer. The course of the disease correlated significantly better with changes in MAM-6 antigen levels than with changes in CEA levels (p less than 0.05), being 79% and 42% respectively. The lower correlation of CEA levels with the course of the disease was mainly due to a lower sensitivity of the CEA assay for advanced breast cancer. The specificity of changing MAM-6 and CEA levels was not significantly different. The main advantage of the MAM-6 assay over the CEA assay is the higher sensitivity of the former. In a preliminary study among stage-IV patients a correlation was found between elevated MAM-6 levels and the presence of the estrogen receptor in the primary tumor.