Annals of Oncology Inverse correlation between anti-MUC1 antibody responses and human CA15 3 levels CA15 3 serum levels were tested in commercial assays for CA15 3 or CA27 29 at each visit Patient serum samples at baseline and at several time points after BrevaRex® mAb-AR20 5 injection were pretreated with a large excess of mAb-AR20 5 (400 μg ml) for 1 h at room temperature to displace anti-MUC1 antibodies