Noninvasive diagnosis of solitary pulmonary lesions in cancer patients based on 2-fluoro-2-deoxy-D-glucose avidity on positron emission tomography/computed tomography.

BACKGROUND: 2-Fluoro-2-deoxy-D-glucose (FDG) imaging is highly accurate for assessing solitary pulmonary nodules (SPNs) in patients without known malignancy. In the current study, the authors evaluated FDG-positron emission tomography/computed tomography (PET/CT) for the characterization of SPN in cancer patients.

METHODS: FDG-PET/CT was performed in 56 cancer patients to evaluate SPNs that measured 15 +/- 8 mm in greatest dimension. The diagnosis was confirmed by histology (n = 34 patients), or by CT or clinical follow-up (n = 22 patients). The performance of PET/CT was calculated for visual and semiquantitative assessment and was related to SPN size, location, histology, and time after initial cancer diagnosis.

RESULTS: Malignancy was diagnosed in 27 of 56 SPNs (48%; 18 second primary tumors and 9 metastases). There were 26 true-positive PET/CT studies (17 second primaries and 9 metastases), 5 false-positive studies, 24 true-negative studies, and 1 false-negative study. The sensitivity of PET/CT for diagnosing malignant SPN in patients with cancer was significantly greater for visual analysis than for semiquantitative analysis (96% vs 89%, respectively; P < .05). Specificity and accuracy were similar for both methods (83% and 89% vs 93% and 91%, respectively). The presence of low-intensity FDG uptake increased the detection rate of malignancy from 4% in non-FDG-avid SPNs to 40%, mainly in second primary tumors. False-positive results were more frequent with lower than mediastinal uptake versus higher than mediastinal uptake (3 of 5 SPNs vs 2 of 26 SPNs, respectively; P < .01) and in SPNs >10 mm.

CONCLUSIONS: FDG imaging was highly accurate for the diagnosis of malignant SPNs in patients with cancer, similar to the general population. The presence of any FDG avidity had significantly greater sensitivity than semiquantitative analysis. The current results indicated that lower than mediastinal uptake should be explored cautiously, particularly for second primary tumors, whereas no FDG avidity was a better predictor of SPN benignity than very low uptake.