Positron emission tomography of lung tumors and mediastinal lymph nodes using [¹⁸F]fluorodeoxyglucose

Positron emission tomography detects increased glucose uptake in malignant tissue using the glucose analogue [2-¹⁸F]fluoro-2-deoxy-d-glucose. We reviewed the scans obtained in 62 patients with lung tumors. All had undergone computed tomography and had tissue-based diagnoses: 22 had adenocarcinomas, 12 had squamous cell carcinomas, 13 had other malignancies, 1 had organizing pneumonia, 1 had a hamartoma, and 13 had granulomas. Positron emission tomography with [2-¹⁸F]fluoro-2-deoxy-d-glucose identified 44 of 47 malignancies. Two of three false-negative findings were tumors that were 1 cm² or less and the other was a bronchioloalveolar carcinoma. All three false-positive findings were granulomas. The sensitivity and specificity of the technique were 93.6% and 80%, respectively, and the positive and negative predictive values were 93.6% and 80%, respectively. The differential uptake ratio was determined in all 62 patients. The mean differential uptake ratio (± the standard error of the mean) for malignant tumors was 6.4 ± 0.56 and that for benign tumors was 1.14 ± 0.26 (p < 0.0001, t test). Twenty-five of the patients had N2 lymph nodes evaluated pathologically. Positron emission tomography with [2-¹⁸F]fluoro-2-deoxy-d-glucose identified negative N2 nodes in 19 of 22 patients (86%) with negative nodes and positive N2 nodes in 2 of 3 patients (66%) with positive nodes, including one instance missed by computed tomography. Positron emission tomography with [2-¹⁸F]fluoro-2-deoxy-d-glucose is a highly accurate and noninvasive method for identifying malignant lung tumors. The clinical application of this imaging technique in the evaluation of N2 lymph nodes awaits the results of ongoing prospective studies.