Discordant findings in patients with non-small-cell lung cancer: absolutely normal bone scans versus disseminated bone metastases on positron-emission tomography/computed tomography.

OBJECTIVE: At present, metastatic bone involvement is usually assessed using bone scintigraphy, which has a high sensitivity but a poor specificity. The objective of our study was to compare the sensibility of the 2-deoxy-2-[18F] fluoro-d-glucose positron emission tomography/computed tomography (F-18 FDG PET/CT) for the detection of bone metastasis in patients with non-small-cell lung cancer (NSCLC) whose technetium 99m methylenediphosphonate (Tc-99m MDP) bone scans were absolutely normal.

MATERIAL AND METHODS: This study based on the retrospective analysis of 95 consecutive patients with histologically proven NSCLC who underwent F-18 FDG PET/CT and Tc-99m MDP bone scan at the Eskişehir Osmangazi University School of Medicine, Department of Nuclear Medicine between November 2006 and October 2008. Nineteen patients (19 of 95, 20%) with absolutely normal Tc-99m bone scan versus multiple high-grade F-18 FDG avid bony metastases on F-18 FDG PET/CT were selected for the review. Their ages ranged from 46 to 73 years (15 males and four females; mean: 57.2 years).

RESULTS: Nine patients had squamous cell carcinoma, six had adenocarcinoma, three had large cell carcinoma and one had adenosquamous cell carcinoma. Tc-99m MDP bone scan that did not reveal bony abnormalities or radiotracer uptake was characteristic of benign disease (defined as absolutely normal) in these patients. Whereas, F-18 FDG PET/CT not only showed extremely disseminated heterogeneous nest-like high-grade FDG avid metastatic foci within the marrow cavity of the upper and lower thoracic spine, lumbar spine, pelvis, rib cages and bilateral proximal long bones, but also showed disseminated osteolytic bony metastases in these areas.

CONCLUSION: Discordant findings of skeletal metastasis between Tc-99m MDP bone scans and F-18 FDG PET/CT imaging may be seen in 20% of the patients with NSCLC. F-18 FDG PET/CT could detect metastatic bone involvement more accurately than bone scintigraphy. Bone scans are insensitive to early bone marrow neoplastic infiltration. Assessment of glucose metabolism with FDG PET/CT can represent a more powerful tool to detect early bone metastases in lung cancer than with traditional bone scans.