Critical considerations on the combined use of 18F-FDG and 18F-fluoride for PET assessment of metastatic bone disease

Cancer metastasizes to the bone marrow and not to the bone: time for a paradigm shift!

“…They show that FDG-PET/CT is superior in lung and breast cancer [ 28 – 30 ]. There is no evidence that the combination of FDG and NaF is warranted except in rare cases, because NaF-PET/CT does not detect more osseous lesions than FDG-PET/CT [ 31 ]. Moreover, NaF PET/CT has other challenges to deal with.…”

“…It has high specificity for osteoblastic lesions, but a generally low specificity is a larger problem with NaF than FDG, as many benign lesions light up for a very long period of time on NaF-PET/CT and because degenerative changes, the most frequent abnormalities depicted by this modality, may have intense and long-lasting NaF uptake, while FDG often shows only weak accumulation. Healed fractures are often FDG-negative, but can remain NaF-positive for a long time [ 31 ]. The literature lacks prospective longitudinal studies with FDG-PET which show the temporal development of bone marrow to bone metastases, and that the changes seen with CT and SPECT during and after chemotherapy treatment do not necessarily represent cancer any longer.…”

18F-FDG PET/CT is a prognostic biomarker in patients affected by bone metastases from breast cancer in comparison with 18F-NaF PET/CT

“…With regard to breast cancer, a higher SUV is associated with various prognostic factors, such as tumour grade, HER2 expression and estrogen receptor (ER) negativity (3,5,28). On the other hand, a strong expression of progesterone receptor (PR) and ER may often be associated with a lower SUV on 18 F-FDG PET/CT (18).…”

Optimizing an 18F-NaF and 18F-FDG cocktail for PET assessment of metastatic castration-resistant prostate cancer

“…One major limitation, which has been recognized by the authors of the studies [9-10], and further pointed out by the Invited Perspective [12] and critical responses to the first large clinical trial with 18 F-NaF/ 18 F-FDG cocktail PET/CT [13-14], is the sub-optimal and not strictly controlled 18 F-NaF/ 18 F-FDG cocktail composition. Static PET/CT imaging with ambiguouos 18 F-NaF/ 18 F-FDG cocktail composition is inferior because the quantification of combined 18 F-NaF/ 18 F-FDG PET/CT images is not possible.…”

“…Static PET/CT imaging with ambiguouos 18 F-NaF/ 18 F-FDG cocktail composition is inferior because the quantification of combined 18 F-NaF/ 18 F-FDG PET/CT images is not possible. If the cocktail for combined 18 F-NaF/ 18 F-FDG imaging procedure was strictly standardized, image quantification with the Standardized Uptake Value (SUV) measure would be possible [9, 13-14]. Although the 18 F-FDG and 18 F-NaF SUV ranges from current clinical practice cannot be directly applied for combined 18 F-NaF/ 18 F-FDG cocktail PET/CT imaging, the combined 18 F-NaF/ 18 F-FDG PET/CT images with controlled cocktail composition would be repeatable and reference SUVs would emerge with a wider adaption of such imaging in clinical practice.…”