Detection of small cell lung cancer bone marrow metastases by tumor stem cell assay

Detection of small cell lung cancer (SCLC) bone marrow (BM) metastases has a prognostic implication in itself and a therapeutic interest in the setting of autologous bone marrow transplantation. In a prospective study involving 68 bone marrow samples, we compared SCLC detection results obtained using a tumor stem cell assay and those obtained using conventional morphology by light microscopy. In agar, tumoral cells were stimulated either by Salmon's conditioned medium or by epidermal growth factor (EGF). Tumoral clonogeneic cells were detected in 11 cases, although 7 of these were considered negative when investigated by light microscopy. On the contrary, metastases were detected by morphology in 8 instances where no growing colonies were revealed by tumor stem cell assay. The choice of stimulating factor did not seem critical since the number of colonies was similar in all the cases. We conclude that the tumor stem cell assay is useful in the detection of small cell lung cancer bone marrow metastases, particularly in cases where these metastases have failed to be recognized through light microscopy investigation. However, the sensitivity of this assay is low and should be complemented by other techniques such as immunodetection.