57Co-bleomycin and 67Ga-citrate in detecting and staging lung cancer

In the investigation of suspected lung cancer bleomycin labelled with cobalt-57 and gallium-67 labelled with citrate are currently used to detect the primary tumour and to establish the presence of metastases in the lung hilum and mediastinum. A comparative study of these radio-pharmaceuticals was performed in 63 patients with proved lung cancer. 57Co-bleomycin showed the primary tumour in 58 patients (92%) and 67 Ga-citrate in 34 (54%) (p less than 0.01). The average tumour-to-lung ratio was 3.4 with 57Co-bleomycin and 1.5 with 67Ga-citrate. Proved metastases in the hilum or the mediastinum were visualised with 57Co-bleomycin scintigraphy in 16 out of 18 patients (89%) and with 67 Ga-citrate scintigraphy in only eight (45%) (p less than 0.01). These results indicate that 57Co-bleomycin scintigraphy is more suitable for detecting and staging lung cancer than is 67Ga-citrate. 57Co-bleomycin is valuable in the detection of peripheral lesions, in which a pathological diagnosis is difficult to achieve, since a positive scintigram indicates malignancy. When 57Co-bleomycin scintigraphy suggests hilar or mediastinal metastases mediastinoscopy should be carried out; but when no metastases are apparent it is reasonable to proceed directly to thoracotomy without mediastinoscopy.