Primary Malignant Bone Tumors (Non-Myeloma)

Assessment of an Equivocal Bone Lesion:

Although malignant bone tumors generally have greater FDG uptake than benign lesions, there are simply too many hypermetabolic benign bone lesions to make PET/CT very useful as an indicator of malignancy or benignity. 

• False Positives: Many benign lesion often demonstrate moderate to intense metabolic activity, including fibrous dysplasia, non-ossifying fibroma, giant cell tumor, aneurysmal bone cyst, Paget’s disease, enchondroma, osteomyelitis, bone infarct and chondroblastoma.
• False Negatives:  Several malignant bone lesions often demonstrate little or no activity, including low-grade chondrosarcoma, plasmacytoma and some myxoid tumors.

To date, the use of PET/CT to confidently distinguish malignant from benign lesions is simply unreliable.

Utility of PET/CT for Known Primary Bone Tumors:

Initial Staging: Permits both assessment of initial disease and serves as a baseline exam for follow up reference. 

• Primary lesion: Size, location and metabolic activity.
• Directs Biopsy: Can sample region of greatest metabolic activity.
• Grading: High-grade vs. low-grade determined by metabolic activity (helps guide therapy and correlates with overall prognosis)
• Regional & Distant Disease: Most commonly to the lungs (also to bones, nodes & brain)

Assessing Response to Therapy & Prognosis: 

• Early Response: Non-responders can be offered alternative therapy.
• Late Response: Assess success or failure of therapy, and ultimate outcome.

Recurrence & Restaging: 

• PET/CT is utilized for patients with known or suspected recurrent disease (or at high risk for recurrence).
• Distinguishing recurrence from post-therapeutic inflammation/scarring at operative site.