ABSTRACT
Mediastinal lymph node metastasis is one of the most important prognostic variables of lung cancer. We designed a study to compare immunoscintigraphy (IS) using iodine-131 anti-carcinoembryonic antigen (CEA) and anti-carbohydrate 19-9 (CA 19-9) monoclonal antibody and computed tomography (CT-scan), in the setting of mediastinal staging. Seventeen patients were involved in a prospective, blind study, to compare IS with CT-scan imaging of the mediastinum. Sensitivity and specificity of both methods were analyzed with reference to pathological staging by mediastinal lymph node sampling. IS imaging was not possible in two patients owing to a thyroid uptake and one patient refused surgery. Among the 14 evaluable patients, sensitivity and specificity were 0.83 and 0.12 for IS, and 0.66 and 0.50 for CT-scan, respectively. We used different thresholds of positivity for both methods in order to evaluate the sensitivity-specificity relationship. When compared with that of IS, the area under the receiver operating characteristic (R.O.C.) curves of the CT-scan was bigger. Although one patient had pathologically confirmed N2 with negative CT-scan and positive IS, the results of IS were hampered by a very high level of false positivity. Finally, there was no relationship between positivity of IS and a high serum CEA level. Lack of specificity and the insufficient sensitivity of the iodine-131 anti-CEA-anti-CA 19-9, lead to the conclusion that IS adds weak information to a CT-scan, in the non-invasive mediastinal staging of lung cancer. More efficient radionuclides and markers are needed in the setting of lung cancer staging.
