Bone marrow metastases in small cell lung cancer: detection with magnetic resonance imaging and monoclonal antibodies.

The detection of bone marrow involvement might be of prognostic value and may influence therapeutic decisions in small cell lung cancer. By unilateral bone marrow aspiration and biopsy, evidence of bone marrow metastases is seen in 15-30% of patients with this disease. Since magnetic resonance imaging of the lower body and immunostaining with monoclonal antibodies have recently been shown to be very sensitive detection methods, we investigated the value of these two techniques in detecting bone marrow involvement in 35 consecutive patients with small cell lung cancer. The results were compared to those obtained with conventional cytohistological analysis. In all cases when cytology and/or bone marrow biopsy were positive, monoclonal antibodies immunostaining and magnetic resonance imaging also detected malignant cells. Furthermore, evidence of bone marrow involvement was shown with magnetic resonance imaging and/or immunostaining in 10 of 26 cases (38%) where routine procedures were unable to detect malignant cells. In one of these 26 patients, magnetic resonance imaging and immunostaining provided the only evidence of metastatic disease. These data suggest that the rate of bone marrow metastases is underestimated by routine procedures. Further investigation is needed to determine whether or not these new non-invasive methods have prognostic value or affect therapeutic choices in small cell lung carcinoma.