Accuracy of FDG PET/CT in the Evaluation of Solitary Pulmonary Lesions—Own Experience

Introduction: In recent years, positron emission tomography (PET) has been increasingly applied in the diagnosis of neoplastic lung diseases. In contrast to conventional imaging studies, PET-CT enables the visualisation of not only the morphology of the suspicious lesion, but also its metabolism. The aim of the present study was to investigate the role of PET-CT in the initial assessment of patients with indeterminate solitary pulmonary lesions. Material and Methods: The study was conducted on a group of 82 patients with indeterminate lung nodule diagnosed at the National Institute of Tuberculosis and Lung Diseases in the period from January 2008 to May 2011. CT and PET-CT were performed in all of the patients. Histological or cytological examination of the biopsy specimens obtained from bronchoscopy, mediastinoscopy and intraoperatively were the reference tests. Results: Malignancy was documented in 40 patients (48.8%). Histopathological analysis of all tumours revealed 12 cases of squamous cell carcinoma, 18 cases of adenocarcinoma and 1 case of carcinoid, whereas in 9 patients the diagnosis of “non-small cell cancer not otherwise specified” was made. All lesions except one were of solid character on chest CT. SUV_max values exceeding 2.5 were found in 38 cancer patients (true positives, TP). The mean value of SUV_max was 9.1 (1–26.8). Forty-two lesions were documented as benign (51.2%). SUV_max values equal to or less than 2.5 were found in 37 patients (true negatives, TN). The mean value of SUV_max in this group was 1.9 (0.5–8.6). The diagnostic value of PET-CT SUV_max exceeding 2.5 in the prediction of neoplastic origin of solitary pulmonary lesions was: sensitivity—95% (95% CI 84–99%), specificity—88% (95% CI 75–95%) and accuracy—91.5% (95% CI 83–96%). Positive predictive value (PPV) was 88.4% (95% CI 76–95%), and negative predictive value (NPV) was 94.8% (95% CI 83–99%). False negative results concerned two patients, with final diagnosis of carcinoid and adenocarcinoma; false positive results were obtained in 5 patients with various inflammatory lesions. Conclusions: In the present study, PET-CT appeared to have high sensitivity (95%), but lower specificity (88%) for predicting the malignant character of solitary pulmonary lesions. Overall diagnostic value of PET-CT SUV_max > 2.5 was high—PPV was 88.4%, NPV was 94.8%. In the authors’ opinion, the PET-CT value may increase when clinical data as well as other radiological documentation (with retrospective assessment) are taken into consideration.