Bone metastases in stomach cancer patients: comparison of Tc-99m HDP scintigraphy and FDG PET/CT scan

To evaluate the values of FDG PET/CT and Tc-99m HDP bone scan in the detection of bone metastases in stomach cancer patients. PET/CT and bone scan images obtained within a month of each other from patients with confirmed stomach cancer, from November 2003 to November 2006, were evaluated. The number and location of the bone lesions were noted. On PET ICT, discrete focal FDG uptake distinguishable from the background cortex or marrow activity was considered a positive finding. The CT portion of the PET/CT was also reviewed for osteoblastic or osteolytic lesions. Confirmation was made by further follow up images with PET/CT, bone scan, CT, and/or MRI. Images of 203 patients were included (69 female, 134 male, average age 60.5 yrs), of which 187 cases were concluded as free from bone metastasis and 16 cases positive for bone metastases. On patient basis, the overall sensitivity, specificity, and accuracy of PET/CT were 99.5%, 87.5%, and 98.5%, and of bone scan were 96.8%, 75.0%, and 95.1 %, respectively. On lesion basis, PET/CT detected more lesions in the cervical vertebrae, while bone scan detected more lesions in the rib cage and skull. There were 5 cases where PET/CT missed lesions seen on bone scan, and the CT portion of the PET/CT demonstrated sclerotic lesions in 3 cases, mixed osteolytic and sclerotic lesion in 1 case, and equivocal finding in 1 other case. In the diagnosis of bone metastasis in stomach cancer patients, PET/CT showed higher accuracy than bone scan. However, bone scan detected more lesions in the ribs and skull. The CT portion of the PET/CT should be carefully examined for osteoblastic metastases