Validation of FDG positron emission tomography for differentiation of unknown pulmonary lesions

Objective The impact of the (2-(fluorine-18)-fluoro-2-2deoxy-D-glucose)-pos itron emission tomography (F-18-FDO-PET) for discrimination of pulmonary le sions was evaluated in a single centre prospective study. Methods: In the s tudy, 109 patients with pulmonary lesions of unknown origin verified by com puted tomography were enrolled consecutively (April 1999-May 2000). They we re subject to F-18-FDG-PET diagnostics. 18F-FDG-PET images were interpreted by two independent nuclear medicine physicians who were blinded to the res ults of other imaging procedures. In 87 patients, surgery was applied follo wed by histological investigation, which served as the gold standard. In 22 other patients, extensive tumour load or assumed benign dignity of the les ions prevented surgery. Results: Overall sensitivity of F-18-FDG-PET in 87 resected patients was 0.86. Differentiation in malignant (n = 69) and benig n lesions (n = 18) revealed sensitivities of 0.9 and 0.72, respectively. Se nsitivity of F-18-FDG-PET in inflammatory lesions was markedly lower (0.43) than in benign tumours (0.91). Standard uptake values were significantly i ncreased in malignant tumours compared with benign lesions (9.9 and 1.6, re spectively; P = 0.035). There was a clear correlation of sensitivity with t umour size with a failure rate of 27% in lesions less than or equal to1 cm (n = 15), 10% (n = 20) in lesions between 1 and 2 cm and 12% (n = 45) above 2 cm. In primary bronchial carcinoma, a clear correlation of sensitivity w as observed with regard to tumour grading (G1, three out of five; G2, 24 ou t of 27; G3, 26 out of 26; and G4, one out of one). Lymph node involvement was correctly suggested in 10 out of 19 (52.6%) patients. However, false po sitive lymph node enhancement was indicated in one out of IS (5.5%) operate d patients with benign lesions and eight out of 39 (20.5%) with bronchial c arcinoma. Conclusion: 18F-FDG-PET at present does not serve as the gold sta ndard for early detection of small and well-differentiated tumours. However , it contributes efficiently to the detection of malignancy in tumours >1 c m, which are moderately or poorly differentiated. Positive lymph node imagi ng must not preclude surgery but requires histological proof. Discriminatio n of benign and malignant pulmonary tumours by F-18-FDG-PET appears to be h ampered in inflammatory lesions. (C) 2001 Elsevier Science B.V. All rights reserved.