Additional effects of FDG-PET to thin-section CT for the differential diagnosis of lung nodules: a Japanese multicenter clinical study.

Objective: This study was a controlled multicenter clinical study on patients with peripheral lung nodules to verify the improvement in the diagnostic ability of FDG-PET when used in combination with thin-section CT (TS-CT).
Methods: Patients with peripheral lung nodules (long maximal diameter: 10-30 mm) detected using CT were examined using TS-CT and FDG-PET for the differential diagnosis of benign or malignant lesions. The primary endpoint was the specificity of the results using a combination of TS-CT and FDG-PET, compared with the results for TS-CT alone. Images were interpreted by investigators at each institution. Blind readings were also performed by an independent image interpretation committee. The gold standard was a pathological diagnosis determined using a surgical or biopsy specimen obtained after PET; and the patients in whom a pathological diagnosis could not be obtained were diagnosed based on a follow-up TS-CT performed more than 6 months later. Adverse reactions to FDG were also evaluated.
Results: The blind reading results for 82 lesions in 81 subjects eligible for analysis among the 90 subjects included in the study showed a specificity of 91.2% (31/34) (95% CI: 76.3-98.1) for TS-CT + PET, compared with a specificity of 67.6% (23/34) (95% CI: 49.5-82.6) for TS-CT alone. The specificity was significantly improved by the addition of the PET findings (p < 0.05). The sensitivity improved from 89.6% (43/48) for TS-CT to 91.7% (44/48) for TS-CT + PET; the addition of PET increased the level of confidence in the diagnosis, but the difference was not significant. The results reported by the institutional investigators were not significantly different. No serious adverse reactions occurred, although two of the 90 subjects exhibited mild adverse reactions.
Conclusions: The addition of FDG-PET to TS-CT for the differential diagnosis of benign or malignant peripheral lung nodules resulted in a significant improvement in specificity. Although a definitive diagnosis of lung nodules requires a histopathological or cytological examination, when combined with TS-CT, FDG-PET can provide additional diagnostic information and improve the specificity.