Positron emission tomography in relation to noguchi's classification for diagnosis of peripheral non-small-cell lung cancer 2 cm or less in size

Backgrond: F-18 fluorodeoxyglucose positron emission tomography (F-18-FDG-PET) scanning has become a critically important tool in diagnosis and management of non-small-cell lung cancer. However, the effectiveness of F-18-FDG-PET as a diagnostic tool for small-sized lung cancer is controversial. The purpose of this study was to examine the accuracy of F-18-FDG-PET in relation to Noguchi's classification in the diagnosis of small peripheral non-small-cell lung cancer. Methods: Between January 2003 and April 2006, 150 patients with peripheral lung lesions who were undergoing chest computed tomography (CT), F-18-FDG-PET, and operation were analyzed. Results: Eighty-three patients had malignant lesions, and 67 patients had benign lesions. PET had a sensitivity, specificity, positive predictive value, and negative predictive value of 75.9%, 64.1%, 72.4%, and 68.3%, respectively. In 37 patients with peripheral lung cancer measuring 2.0 cm or less in the greatest diameter, the sensitivity was 51.4% and the specificity was 51.9%. Among them, all 4 cases of Noguchi type A adenocarcinoma [localized bronchioloalveolar carcinoma (LBAC)], 4 of 5 type B and 8 of 17 type C were false negative, while 9 of 11 (81.8%) types D, E, and F (invasive carcinomas without a BAC component) were true positive. Conclusion: The accuracy of F-18-FDG-PET is generally low in distinguishing malignancy from benign lesions in small lesions (< 2.0-cm diameter). The significance of PET as a diagnostic tool is small, especially when the tumor has a ground-glass component at a high rate. The sensitivity of PET is high in small invasive carcinomas without a BAC component, but it is difficult to distinguish carcinoma from benign tumor from its image.