RT Journal Article
SR Electronic
T1 Bone and bone marrow PET imaging of metastatic bone disease: Indirect and direct methods of assessment
JF Journal of Nuclear Medicine
JO J Nucl Med
FD Society of Nuclear Medicine
SP 2037
OP 2037
VO 62
IS supplement 1
A1 William Raynor
A1 Donald Detchou
A1 Austin Borja
A1 Mahdi Zirakchian Zadeh
A1 Siavash Mehdizadeh Seraj
A1 Thomas Werner
A1 Mona-Elisabeth Revheim
A1 Abass Alavi
YR 2021
UL http://jnm.snmjournals.org/content/62/supplement_1/2037.abstract
AB 2037Objectives: 1. Review the PET tracers and their targets in evaluating metastatic bone disease. 2. Evaluate the relative utility of imaging bone turnover compared to imaging tumor-specific metabolic activity. Methods: Bone metastases often result from tumor cells that seed the red bone marrow and eventually cause bone remodeling through the activation of osteoclasts, osteoblasts, or both. PET imaging with 18F-sodium fluoride (NaF), along with the related approach of bone scintigraphy using 99mTc-labeled tracers, has received widespread use in identifying sites of increased osteoblastic activity in response to metastasis involving bone. However, because these modalities show cellular activity in response to tumor cell activity rather than activity of tumor cells themselves, information derived from these images can only constitute indirect evidence for presence of metastasis. Because tumor cells often possess high glycolytic activity, PET imaging with 18F-fluordeoxyglucose (FDG) is typically an appropriate tracer to detect the presence of tumor cells in the bone marrow. Evidence suggests that osteolytic lesions, such as those found in breast cancer, are particularly FDG-avid, resulting in excellent sensitivity and specificity. However, because certain phenotypes of prostate cancer result in low uptake of FDG by cancer cells, imaging with other PET tracers is warranted in such cases. Choline labeled with the isotopes 18F and 11C as well as prostate-specific membrane antigen (PSMA) ligands labeled with 68Ga and 18F are feasible methods of accurately detecting bone metastases from prostate cancer. Results: The fact that NaF-PET is limited to bone-specific rather than tumor-specific activity has significant clinical implications because small intramedullary lesions that have not caused changes in bone turnover will not be detected. Furthermore, purely lytic lesions will not cause focal NaF uptake, which only reflects osteoblastic activity. The flare phenomenon, in which successfully treated metastases demonstrate focal NaF uptake due to physiologic healing, is a known cause of false positive findings. The vast majority of malignant conditions result in high FDG uptake due to the Warburg effect exhibited by most cancer cells. As a result, hybrid imaging consisting of FDG-PET combined with CT or MRI will be the modality of choice for staging many types of cancer, including evaluating for bone metastases. The low uptake of FDG seen in prostate cancer necessitates other tracers such as radiolabeled choline and PSMA ligands to facilitate accurate imaging of potential malignant activity in the bone marrow. Conclusions: Although bone metastases are commonly evaluated by bone-specific agents, the proposed paradigm shift of using tumor-specific PET tracers will result in greater sensitivity and specificity in identifying bone metastases and monitoring their response to therapy.