RELIABILITY OF GALLIUM SCAN CHEST RADIOGRAPHY COMPARED TO MEDIASTINOSCOPY FOR EVALUATING MEDIASTINAL SPREAD IN LUNG-CANCER

Abstract

Mediastinoscopy had become a major staging procedure for characterizing mediastinal and hilar tumor spread in lung cancer. Many patients are now identified as having a nonresectable lesion and are saved the possible morbidity and mortality of full thoracotomy. To achieve this advance, as many as 1/2-2/3 of all ptients (i.e., those with a negative mediastinoscopy) are subjected to 2 procedures: mediastinoscopy followed by thoracotomy. In an attempt to decrease the number of staging mediastinoscopies, recent reports dealt with the degree of correlation between chest roentgenography and mediastinoscopy and concluded that patients with a normal mediastinum on the chest film may be spared a staging mediastinoscopy. This investigation deals with an evaluation of another noninvasive technique, Ga scanning of the lung and mediastinum, in the staging of lung cancer. The degree of correlation between Ga scans, chest roentgenography and mediastinoscopy was reported in a prospective study of 31 patients with primary lung cancer, with potential resectable cell type (patients with oat cell carcinoma were excluded as having nonsurgical disease). The primary lesion concentrated Ga in 25 of patients; in 6 it did not. Imaging of the mediastinum for Ga in these 25 patients allowed a comparison between these 2 noninvasive techniques (Ga scan and chest radiography) and mediastinoscopy. The true-positive ratio for Ga scan (i.e., the ratio of the number of true-positive Ga scans to the number of true-positive mediastinoscopies) was 100%. The true negative ratio (i.e., the ratio of the number of true-negative Ga scans to the number of true-negative mediastinoscopies) was 71%. The following diagnostic approach to the preoperative staging of lung cancer is recommended. If the chest roentgenogram suggests mediastinal spread, mediastinoscopy should be performed to obtain tissue confirmation of such spread. If the chest film shows no mediastinal abnormality, a Ga scan should be obtained, and if the primary tumor concentrates Ga and the mediastinum does not, the patient may be spared a staging mediastinoscopy and be referred directly for thoracotomy. If both primary lesion and mediastinum pick up Ga or the primary lesion does not concentrate Ga, the patient should be subjected to a staging mediastinoscopy.