Metastatic Disease: Skeletal Surveys and Bone Scans

Lytic lesions must cause at least 30%-50% demineralization to be visible by radiography. Bone scan is much more sensitive in detecting metastatic lesions in some cancers, and not so great in others. Conditions that have high false negative rates on bone scan include:

• Multiple myeloma
• Renal cell carcinoma
• Thyroid carcinoma
• Langerhans cell histiocytosis
• Neuroblastoma
• Highly aggressive anaplastic tumors
• Reticulum cell sarcoma

False positivity for metastatic disease is also high when a single lesion is seen. In patients with known malignancy and no benign radiographic explanation for a bone scan lesion, additional workup is necessary. Some statistics:

• A single spinal lesion on bone scan has a 10%-20% chance of representing a metastatic focus.
• A single rib lesion on bone scan has a 10% chance of representing a metastatic focus. Lesions in consecutive ribs are almost always traumatic in origin. Lesions in nonconsecutive ribs have a high chance of representing metastatic disease.
• An isolated sternal lesion on bone scan in a patient with breast cancer, on the other hand, has an 80% chance of representing a metastatic focus.

In the case of prostate cancer, PSA level < 10 μg/L is a good predictor of a negative bone scan.

References

• Gleave ME, Coupland D, Drachenberg D, Cohen L, Kwong S, Goldenberg SL, Sullivan LD. Ability of serum prostate-specific antigen levels to predict normal bone scans in patients with newly diagnosed prostate cancer. Urology. 1996 May;47(5):708-12.
• Kwai AH, Stomper PC, Kaplan WD. Clinical significance of isolated scintigraphic sternal lesions in patients with breast cancer. J Nucl Med. 1988 Mar;29(3):324-8.
• Mettler FA and Guiberteau MJ. Chapter 9. In Essentials of Nuclear Medicine Imaging. Fifth Edition. Saunders, Philadelphia. 2006. p 250.
• Tumeh SS, Beadle G, Kaplan WD. Clinical significance of solitary rib lesions in patients with extraskeletal malignancy. J Nucl Med. 1985 Oct;26(10):1140-3.