Evolving concept of imaging bone marrow metastasis in the twenty-first century: critical role of FDG-PET

Excerpt

In this communication, we have explored the role of modern imaging modalities in investigating skeletal involvement by cancer. Obviously, detecting and characterizing disease sites at early stages are most desirable for the early and accurate assessment of disease activity. Based on the differences in physical and biological principles of each of these imaging modalities, they can be broadly categorized into two groups: those that detect the disease sites at the “bone marrow” (BM) level and those that rely on indirect evidence including osteoblastic reaction after invasion of the surrounding bone by the pathologic process. We further subclassify the first group of methodologies into two categories: those that visualize lesions as negative focal marrow defects as seen on BM scintigraphy (BMS) or MRI, and those that are based on targeting of abnormal tissue directly such as with fluorodeoxyglucose (FDG) positron emission tomography (PET) imaging. The emergence of the latter method combined with whole-body tomographic imaging has truly revolutionized diagnosis and staging of patients with cancer and other serious disorders. This is particularly true for FDG-PET imaging, which is now commonly employed. It is imperative to understand the significance and implications of the osseous abnormalities visualized by FDG-PET as opposed to those seen by either structural (CT or MRI) or other functional imaging modalities (bone scintigraphy). Inappropriate interpretation of the results from these distinctly different types of imaging studies has resulted in misunderstanding of the optimal utility of different approaches. In this communication, we shall make an effort to clarify the underlying concepts that are related to this subject and the controversies that are reported in the literature. …