Increased alpha-fetoprotein receptor in the serum of patients with early-stage breast cancer

The alpha-fetoprotein (AFP) receptor (RECAF) is an oncofetal antigen found in most types of cancer. Using a competitive radioimmunoassay, we measured the concentration of serum RECAF in three sets of samples. Set 1 was blind and consisted of 119 normal subjects, 43 breast cancer patients (stages I and 1), and 20 patients with benign breast conditions. In this set, the assay discriminated normal from cancer samples with a receiver operating characteristic for the area under the curve (ROCAUC) of 0.983; with 95% specificity and 93% sensitivity at a cut-off of 4.6 K (arbitrary) RECAF units; and with 72% sensitivity and 100% specificity at a cut-off of 7.3 K units. At 7.3 K units, the specificity for benign breast conditions was 85%, and the sensitivity was 72% (ROCAUC was 0.773). Carcinoembryonic antigen and cancer antigen 15-3 respectively showed 39% and 41% sensitivity, with 95% specificity in comparisons of normal with cancer samples, and 34% and 44% sensitivity, with 85% specificity in comparisons of benign with cancer samples. Set 2 consisted of 353 normal, 30 benign, and 64 cancer samples (stages II and in). The RECAP assay sensitivity in discriminating normal from cancer samples was 97%, with 97% specificity. Benign compared with cancer samples showed 87% sensitivity, with 97% specificity. Set 3 included only 40 normal and 40 cancer samples. The assay sensitivity was 89%, with 100% specificity. Sets 2 and 3 were not tested with carcinoembryonic antigen and cancer antigen 15-3. These results strongly suggest that the RECAF assay could be used for detecting breast cancer in its early stages.