Bone and Gallium scintigraphy in primary malignant and benign bone tumors of the extremities

A six yer prospective evaluation of 129 patients suspected of having a primary bone tumor included Tc-99m MDP bone scintigraphy followed by Ga-67 imaging at 48-72 hours. Blood pool images were part of bone scintigraphy in nearly half of the patients. Extent and intensity of tracer uptake in tumor and adjacent bone and joints were recorded for each tracer by two observers blind to the diagnosis. Tissue samples obtained in every patient by biopsy or tumor excision after scintigraphy, revealed 72 malignant and 57 benign bone tumors. The bone scan was positive in 95% (69/72) of malignancies. The scintigraphic intensity of benign and malignant lesions was comparable with both Tc-99m MDP and Ga-67. On the other hand, bone scintigraphy showed 72% (52/72) of bone malignancies to have abnormal proximal and distal bone/joint uptake whereas the Ga-67 images revealed this in only 6% (4/65) of malignancies. Benign lesions manifested this enhanced contiguous bone/joint uptake on only 8% (5/55) of bone and 0% of Ga-67 scans. This study concludes positive bone, blood pool, or Ga-67 images have less specificity for malignancy than the presence of increased Tc-99m MDP deposition in a contiguous bone/joint, but negative scintigraphic results strongly favor a benign lesion.more » Ga-67 was more accurate than Tc-99m MDP in portraying intraosseous extent of malignant tumors; however, this is now preferably done with C.T.« less