Anti-CEA immunoscintigraphy and computed tomographic scanning in the preoperative evaluation of mediastinal lymph nodes in lung cancer

Background - Thoracic computed tomography (CT) provides most of the staging information needed before operation for lung cancer and can reduce the number of exploratory thoracotomies. In recent years a new immunoscintigraphic technique with anti-carcinco embryonic antigen (CEA) monoclonal antibodies has been shown to be effective in lung cancer staging. This study compares the yields of CT scans and immunoscintigraphy in the preoperative evaluation of the mediastinal lymph nodes of patients with non-small cell lung cancer. Methods - One hundred and thirty one patients believed on clinical grounds to have an operable non-small cell lung cancer were photoscanned with the indium-111 labelled F(ab')2 fragments of the antibody FO23C5. Both planar and single photoemission computed tomography (SPECT) thoracic views were recorded. CT scans of the thorax, abdomen, and brain were obtained in all patients. Seventy of the patients eventually underwent surgery, an additional seven underwent mediastinoscopy or mediastinotomy, and a further 10 had both cervical exploration and thoracotomy. Pathological evaluation of the mediastinal nodes was available in all 87 patients, but in only 80 of them was the diagnosis of lung cancer eventually confirmed. Results - The diagnostic accuracy of planar immunoscintigraphy, SPECT immunoscintigraphy, and CT scanning for N2 disease was 76%, 74%, and 71%, respectively. The corresponding sensitivity and specificity rates were 45%, 77%, 64% and 88%, 72%, and 74%. These were not significantly different. Conclusions - This study shows that anti-CEA immunoscintigraphy has no advantage over conventional CT scanning in assessing mediastinal lymphoadenopathy in patients with lung cancer. CT scanning remains the gold standard test in these patients.