Computed tomography: an effective technique for mediastinal staging in lung cancer. Discussion

Computed tomographic scans of the chest were utilized to stage mediastinal disease in 148 instances of bronchogenic carcinoma considered for resection in 146 patients. Nodes ≥ 1.5 cm in diameter were interpreted as abnormal. All nodes positive by computed tomography were evaluated by mediastinoscopy, anterior mediastinotomy, or thoracotomy. All patients with negative computed tomographic findings underwent thoracotomy without prior surgical staging. Patients undergoing thoracotomy were divided into two groups. In Group I (first 51 instances) routine mediastinal exploration was not carried out; in Group II (last 97 instances) the mediastinum was explored in every patient and nodes were submitted for histopathological study. The computed tomographic and pathological findings on the mediastinal lymph nodes were compared. The sensitivity, specificity, and accuracy of computed tomography in Group I were 88%, 94%, and 92%, respectively, in Group II 75%, 89%, and 86%, and in the combined group, 80%, 91 %, and 88 %. The positive predictive index in Group I, Group II, and in the combined group was 88%, 69 %, and 77 %, respectively. It was lower for central than peripheral lesions (74 % versus 88 %) and was lowest for lesions in the right upper and left lower lobes. The negative predictive index was greater than 90% for all groups and all tumor sites except the left upper lobe, where it was 89%. Ten patients had false-positive scans, three with old mediastinitis and seven with postobstructive pneumonia; nine of the 10 had central lesions, and seven of these lesions were located in the right upper lobe. Eight patients had false-negative scans; six had para-aortic, subaortic, or postsubcarinal nodes. These nodes would not have been accessible to mediastinoscopy. In only one patient with false-negative nodes would routine mediastinoscopy have prevented thoracotomy and resection. Computed tomographic staging of mediastinal disease is indicated for all patients with lung cancer in whom operation is contemplated. Computed tomography directs the most appropriate staging procedure for patients with positive findings and obviates invasive staging for patients with negative findings.