Mediastinal Lymph Node Involvement in Non–Small Cell Lung Cancer: Evaluation with 99mTc-Tetrofosmin SPECT and Comparison with CT

In patients with non-small cell lung cancer (NSCLC), surgical resection offers the best chance of cure. The preoperative assessment of mediastinal lymph node involvement is crucial to selecting those patients for whom surgery is indicated. Methods: To evaluate the possible clinical role of Tc-99m-tetrofosmin scintigraphy in the presurgical detection of mediastinal node metastases from NSCLC, we performed a prospective comparative study with CT on 83 patients (48 men, 35 women; age range, 38-81 y) with primary NSCLC (36 adenocarcinomas, 39 epidermoid squamous cell carcinomas, and 8 large cell anaplastic carcinomas). They underwent chest SPECT 20 min after Tc-99m-tetrofosmin injection (740 MBq intravenously). The metastatic involvement of mediastinal nodes was assessed by histologic examination after mediastinoscopy or thoracotomy. Both chest CT and Tc-99m-tetrofosmin scintigraphy were performed within 2 wk before the surgical staging. Results: Metastatic mediastinal lymph nodes were found in 35 patients. Tc-99m-Tetrofosmin imaging in assessing the mediastinal involvement yielded a sensitivity of 85.7%, a specificity of 89.6%, and an accuracy of 88.0%; CT results were 68.6%, 75.0%, and 72.3%, respectively. SPECT accuracy was significantly higher than CT accuracy (P < 0.05). However, precise anatomic localization of Tc-99m-tetrofosmin uptake in the mediastinum was not always present on SPECT images. Tc-99m-Tetrofosmin SPECT precisely detected the presence or absence of lymph node metastases in 33 of the 36 patients with positive CT findings (enlarged mediastinal nodes with a short axis greater than or equal to 1 cm), with an accuracy (91.7%) significantly higher (P < 0.05) than that of CT (66.7%). Conclusion: Tc-99m-Tetrofosmin SPECT is a useful presurgical noninvasive method to assess mediastinal lymph node involvement in NSCLC. In particular, it could play a clinical role in reducing the number of invasive staging surgical procedures in selected patients, especially in those with enlarged lymph nodes at CT. Fusing SPECT with CT images could further improve the interpretation of the scintigraphic data.