Selective decrease of serum immunoglobulin G1 as marker for early stages of invasive breast cancer

The diagnostic value of the decrease in percentage of immunoglobulin G1 (%lgG1) in breast cancer was analyzed with special emphasis on early tumor stages. IgG1 and total IgG were preoperatively measured in the sera of a total of 801 individuals using a modified quantitative affinity chromatography. Group A consisted of 174 healthy individuals of both sexes, group B of 324 female patients with benign breast disease, and group C of 303 patients with invasive and non-invasive breast cancer. Within group C, 13 patients presented with intraductal carcinoma, and 22 patients with a pT1a-tumour (diameter less than 0.5 cm). The %IgG1 values were compared among groups A, B and C. In addition, correlations were sought between %IgG1 values of group C and tumor size, stage (UICC), histopathological grade and oestrogen (ER) and progesteron receptor (PR) expression. The mean value of %IgG1 in group A was 63.3 +/- 0.5 s.e.m., in group B 57.75 +/- 0.4 s.e.m. and in group C 52.37 +/- 0.5 s.e.m. The differences of mean values were highly significant between all three groups. Sensitivity and specificity of %IgG1 to discriminate between group A and C were 75% and 87%, and between group B and C 62% and 63%, respectively. The significant decrease of %IgG1 in total serum IgG is able to distinguish patients with breast cancer of more than 5 mm in diameter from healthy controls and patients with benign breast diseases. Finally, calculated posterior probabilities revealed that within certain concentration limits %lgG1 may provide predictive information with high probabilities.