Is (99m)Tc-MDP whole body bone scintigraphy adjuvant to (18)F-FDG-PET for the detection of skeletal metastases?

Purpose: Due to the fact that fluorine-18-fluorodeoxyglucose positron emission tomography/computed tomography ((18)F-FDG-PET/CT) and technetium-99m-methylenediphosphonate ((99m)Tc-MDP) whole body scans identify bone metastases by different mechanisms, i.e. by using glucose metabolism and osteoblastic response in the bone, respectively, it can be expected that there may be some differences between these two methods in the number of lesions identified. The aim of this study was to compare the sensitivity, specificity, accuracy, positive predictive value (PPV) and negative predictive value (NPV) in detecting bone metastases between (18)F-FDG-PET/CT and conventional (99m)Tc-MDP whole body scans.

Methods: Between 2006-2009, 121 patients with malignancies (62 male and 59 female, mean age 59.3±10.8 years, range 37-84) were examined with (18)F-FDG-PET/CT and conventional (99)Tc-MDP whole-body scans for detection of bone metastases.

Results: For (18)F-FDG-PET/CT and for (99m)TC-MDP, sensitivity, specificity, accuracy, PPV and NPV for detecting all studied bone metastases were 88.3, 83.6, 86.7, 91.7, 77.8% and 91.7, 71.0, 84.9, 86.6, 80.8%, respectively. For bone metastases of breast and lung cancers, the specificity and accuracy of PET/CT was higher than that of bone scintigraphy. On the other hand, the sensitivity of bone scintigraphy was higher than PET/CT in breast and lung cancers groups and all patients. In the detection of osteolytic and osteosclerotic metastases no difference was found between the two methods, while for osteolytic lesions the mean standardized uptake value (SUV) max was higher than for osteosclerotic lesions.

Conclusion: For the detection of bone metastases the specificity and accuracy of (18)F-FDG-PET/CT were higher compared to bone scintigraphy, while the sensitivity was lower. It is the opinion of the authors that both studies are complementary to final diagnosis.