Immunodetection of small cell lung cancer metastases in bone marrow using three monoclonal antibodies

Detection of bone marrow metastases by indirect immunofluorescence methods was investigated using three monoclonal antibodies (MoAbs) raised against small cell lung cancer (SCLC). These antibodies, designated anti-LCA1, -LCA2 and -LCA3, recognize three different antigens on the surface of SCLC cells. Eighty-four bone marrow samples from 74 different patients were studied. Whereas tumor cells were found in 32 (38%) by MoAb staining, only 10 (12%) were positively identified using conventional morphological methods. Nine out of the morphologically positive specimens showed reactivity with at least two monoclonal antibodies. Among the 32 samples proven positive by immunofluorescence, an important antigenic variability was noted. Anti-LCA1 recognized tumor cells in 62%, anti-LCA2 and anti-LCA3 in 53%. Due to the recognition of bone marrow involvement by fluorescence methods in 26% of the 34 patients classified as limited disease, a new subgroup of limited disease patients was defined whose prognosis remains undetermined. Our results confirm the utility of immunodetection in the diagnosis of SCLC bone marrow metastases and emphasize the advantage of using a panel of MoAbs with different antigenic specificities. Further study is needed to determine the prognostic significance of bone marrow involvement established by immunodetection.