The diagnostic role of FDG PET/CT in pulmonary lesions larger than 1 CM

Radiography and computed tomography are frequently used noninvasive imaging methods in the evaluation of the lung lesions. Several radiological parameters are used for differentiating benign pulmonary lesions from malignant ones. But these parameters are not always helpful for the differentiation. Recently FDG PET/CT has become an established imaging method in oncology and evaluates metabolism of lesions. The aim of our study was to determine diagnostic value of FDG PET/CT in assessing the malignant potential of pulmonary lesions described on thorax CT. Between January 2010 and December 2012 213 patients (182 males, 31 females) who had pulmonary lesions larger than 1 cm in diameter on thorax CT and underwent PET/CT scan in the Nuclear Medicine Department of Gaziantep University Hospital were included in the study. Because of limited spatial resolution of PET/CT, patients who had lesions smaller than 1 cm were excluded from the study. We accepted lesions as malignant if the lesion's SUVmax value higher than 2.5. FDG PET/CT images and patients' files were analyzed retrospectively, then we calculated the sensitivity, specificity, PPV and NPV of FDG PET/CT. PET/CT showed hypermetabolic lesions in 188 patients and hypometabolic lesions in 25 patients. One hundred and sixty two patients had malignant pathology and 51 patients had benign pathology according to histopatologic studies and radiological follow-up. In malignant group, 143 patients were diagnosed as NSCLC, 17 patients were diagnosed as SCLC, 2 patients were diagnosed as metastasis. Sensitivity, specificity, PPV and NPV of PET/CT were calculated as 100%, 49%, 86%, and 100%, respectively. In patients who had lesions smaller than 3 cm we found that sensitivity, specificity, PPV and NPV were 100%, 66.6%, 78% and 100%, respectively. In lesions larger than 3 cm we found that sensitivity, specificity, PPV and NPV were 100%, 29% 88% and 100%, respectively. In conclusion, FDG PET/CT sensitivity is high in evaluation of pulmonary lesions. If compared to literature, our specificity is low. In our study false positive pathologies decreased the specificity. In our country especially in our region granulomatous diseases (tuberculosis, sarcoidosis) are frequently seen and they can cause false positive results. Therefore, when we detect a hypermetabolic lesion in the lung on FDG PET/CT, we should consider that some of these hypermetabolic lesions may be related to a benign pathology. Key Words: FDG PET imaging, Sensitivity, Specificity, Lung Cancer.