Metastatic Bone Disease

Metastatic tumors develop when cancer cells break off from a primary tumor and enter the bloodstream. These cells can reach nearly all tissues in the body, and bones are a common place for these cancer cells to settle and start growing. More than 90% of all these metastatic lesions in bone are caused by a small number of primary tumors, including breast, lung, kidney, prostate, and thyroid. 


It is extremely important in the diagnosis and staging of these cancers to determine the true extent of the disease and whether the tumor has spread to the skeleton. The patient’s prognosis, or the outlook for recovery, depends upon determining the stage of the cancer and the best treatment options. For early cancer, surgery may be all that is needed, and so it is critical to exclude the presence of any bone metastases before the potentially curative surgery is performed. For cancer that is more advanced, chemical or radiation therapy may be needed as well to increase the chance of a cure or delay the cancer's progression. After treatment is complete, it is important to know if any active cancer cells remain in the body. This is called restaging. 


A whole-body sodium fluoride F 18 (18F NaF) bone PET/CT scan can be performed before treatment to help the physician determine the most appropriate treatment, and after treatment to help determine the effectiveness of the treatment, to image the tumor’s response to therapy and to detect recurrence in treated lesions. 





Bone Imaging


A PET/CT scan with sodium fluoride F 18 injection (18F NaF) is a nuclear imaging test that scans the entire skeletal system and produces high-resolution images of the bones. These images are used to detect areas of abnormal bone growth associated with tumors. 


A bone scan is an important tool for detecting cancer that has metastasized or spread to the bone from a tumor that started in a different organ, such as the breast or prostate. 


Some of the most prevalent cancers in the United States are commonly associated with metastatic bone disease. This is of particular clinical importance in breast and prostate cancers because of the prevalence of these diseases. At postmortem examination, 70% of breast and prostate cancer patients had evidence of metastatic bone disease.1 However, bone metastases are not restricted to only these two cancers. They may complicate a wide range of other malignancies, resulting in considerable morbidity and complex demands on health care resources. Carcinomas of the thyroid, kidney, and lung also commonly give rise to bone metastases, with an incidence at postmortem examination of 30% to 40%.1 


18F NaF bone imaging provides the physician with physiologic information of the bone. Live adult bone is not a rigid inorganic framework. At millions of microscopic sites throughout the skeleton, and especially at areas of disease, bone is constantly being broken down and then remade in a cellular process termed remodeling. When the PET scan shows areas of increased uptake of 18F NaF in the skeleton, it reflects sites of increased blood flow and bone remodeling. This information can be used by physicians to diagnose bone disease, detect bone injury or determine the extent of metastatic disease. 


A bone PET/CT scan's high-resolution images and its ability to scan the entire skeleton make it very helpful in detecting areas of abnormal bone growth associated with tumors. The test poses no greater risk than do conventional x-ray procedures, as the radiopharmaceutical used produces very little radiation exposure. 


Effective February 2011, the Centers for Medicare and Medicaid (CMS) began covering 18F NaF PET scans as part of the National Oncologic PET Registry (NOPR). 



  1. Galasko C. The anatomy and pathways of skeletal metastases. In: Weiss L, Gilbert A, editors. Bone metastases. Boston: GK Hall; 1981. p. 49 - 63.


PET/CT Utilization


Sodium fluoride F 18 (18F NaF) bone PET/CT imaging is a noninvasive test that physicians utilize to stage the body for the presence or absence of active bone tumors, localize the tumors, assess the tumors' response to treatment and detect recurrence in treated lesions. 


PET/CT Utilization in Metastatic Bone Disease

  • Identifying skeletal metastases in patients with a range of primary tumors
  • Performing initial evaluation and staging of metastatic disease in the skeleton
  • Localizing metastatic bone disease
  • Characterizing benign or malignant lesions in patients at risk for bone metastases
  • Assessing response of skeletal metastases to therapy
  • Detecting skeletal metastases during follow-up
  • Detecting primary tumors of the bone and identifying sites of disease
  • Assessing response to therapy in primary bone tumors
  • Detecting recurrent disease in primary bone tumors 

Source: Grant. 2008. Skeletal PET with 18F-Fluoride: Applying New Technology to an Old Tracer JNM 2008; 49(1):68-78 


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