Mechanisms of levamisole-induced granulocytopenia in breast cancer patients.

Five of 39 (13%) women treated with adjuvant combination chemotherapy plus levamisole immunotherapy after mastectomy for Stage II or III breast cancer developed levamisole-induced granulocytopenia. This complication occurred in each of the women between six and ten weeks after the completion of six months of combination chemoimmunotherapy when they were taking levamisole alone. Although none of the patients had an HLA B-27 locus and leukoagglutinins could not be demonstrated, complement-dependent, IgM mediated, peripheral destruction of granulocytes was documented using a microgranulocytotoxicity assay. In addition, a factor(s) present in serum from patients developing levamisole-induced granulocytopenia caused suppression of bone marrow granulocyte progenitor cells (CFU-C). The possible relationships between levamisole-induced peripheral granulocyte destruction and bone marrow CFU-C suppression are discussed.