A prospective study of circulating immune complexes in patients with breast cancer

Levels of circulating immune complex (cIC) and complement split product C3d were studied in 86 patients with breast cancer (BC), 22 patients with benign breast disease (BD), and 72 age- and sex-matched blood-bank donors (NC), using solid-phase Clq-protein A RIA, Clq-anti-IgG RIA, anti-C3d anti-IgG RIA, and polyclonal IgM-rheumatoid factor ELISA for clC detection. No significant differences in cIC and C3d levels were found between the groups. The incidence of raised cIC levels varied from 4.9 to 8.2% in the BC group and from 4.5 to 22.7% in the BD group in comparison with 2.9 to 3.0% in the NC group. Using the solid-phase polyclonal IgM-rheumatoid factor ELISA we found that the cIC levels of patients with stage-III cancer were significantly higher than those of patients with stage-I or stage-II cancer. However, the other tests showed no relationship to tumor burden. Likewise, an effect of mastectomy on the cIC levels was also only detectable by one of the assays, i.e., the post-mastectomy levels of cIC as measured by the solid-phase anti-C3d anti-IgG RIA were significantly lower than the pre-mastectomy levels. Serial analyses of cIC and C3d levels were performed pre-operatively, one month post-operatively and every 3 months during the first year after mastectomy in 46 of the patients. During a I-year observation period, 7 patients developed metastatic disease. The occurrence of metastatic disease was not, however, preceded by characteristic changes in serially determined cIC and C3d levels.