INTERFERENCE BY HUMAN-ANTIBODIES WITH TUMOR-MARKER ASSAYS

Many cancer patients respond to the in vivo application of murine mono clonal antibodies with the formation of various human antibodies which can interfere with tumor marker assays, While interferences by nonspe cific human anti-mouse antibodies can be eliminated by addition of non specific mouse IgG, special problems can occur when the antibody appli ed in vivo also is employed in the in vitro assay, In ovarian cancer p atients treated with the anti-CA-125 antibody OC125 and with the anti- TAG-72 antibody B72.3, respectively, we measured erroneous values for the tumor associated antigens CA-125 and TAG-72 due to human antiidiot ypic or antiantudiotypic antibodies, These interferences can only be p revented by using reagent antibodies different from the antibody appli ed in vivo. However, because it is difficult to eliminate interference s completely, tumor marker values determined in patients treated with monoclonal antibodies should be interpreted with care.