Mediastinal Staging of Non-Small-Cell Lung Cancer

Computed Tomography/Magnetic Resonance Imaging

Computed tomography is currently used to radiographically stage the mediastinum in patients with primary bronchogenic cancer. The accuracy of CT in staging the mediastinum has been controversial over the last 20 years largely due to variability of patient selection and study design. Mediastinal nodes larger than 1 cm on short axis are defined as pathologic.^[7] One objective of CT is to identify patients who do not have mediastinal disease so they can proceed to resection without the need for further mediastinal staging.It has been reported that 3% to 16% of patients with mediastinal lymph nodes less than 1 cm on CT have tumor involvement at mediastinoscopy, thus rendering them unresectable.^[8,9] A goal of preoperative staging with CT is to spare patients with known mediastinal involvement the morbidity of surgical staging.This may not be possible as up to 30% of patients with enlarged nodes on CT do not have evidence of neoplastic disease at surgical exploration of the mediastinum.^[10] Put simply, if all lymph nodes greater than 1 cm were assumed to be cancerous, 30% of patients with otherwise resectable tumors would be denied potentially curative surgery.

Several factors affect the accuracy of CT for staging bronchogenic carcinoma. Accuracy is lessened by central tumors, obstructive pneumonia, and prior granulomatous disease. Peripheral tumors may increase the accuracy.^[8] A meta-analysis of CT accuracy for assessment of mediastinal lymph node involvement in bronchogenic carcinoma found an overall sensitivity and specificity of 79% and 78%, respectively.^[11]

Magnetic resonance imaging (MRI) is often helpful in evaluating direct invasion of tumor into mediastinal structures including the heart, superior vena cava, aorta,and subcarinal area. With respect to staging of mediastinal lymph nodes, MRI has been shown to be no better than conventional CT imaging. It suffers from limited spatial resolution and the inability to obtain images during held respiration. This can lead to blurring of separate lymph nodes into one large node. A thorough review of this modality is reported elsewhere.^[12]

Cancer Control. 2001;8(4) © 2001  H. Lee Moffitt Cancer Center and Research Institute, Inc.