The value of quantitative analysis in ¹⁸F-NaF PET/CT

To evaluate the ability of SUVmax to differentiate bone metastases from degenerative lesions, blastic from lytic metastases, as well as to determine the correlation between SUVmax with ¹⁸F-NaF and with ¹⁸F-FDG.

A review was performed on 115 ¹⁸F-NaF PET/CT studies. Of the 64 patients with bone metastases, 49 (39 women, 10 men, 61±12 years (16-81)), in whom the PET/CT supported the diagnosis of bone metastases, were selected for analysis. A record was made of the SUVmax of a maximum of ten metastases in each patient (total 172: 141 blastic, 31 lytic), as well as four degenerative lesions (total 188) with the greatest ¹⁸F-NaF uptake intensity. Of the 49 patients analyzed, 43 also had a ¹⁸F-FDG PET/CT performed in which a record was made of the SUVmax values for ¹⁸F-FDG calculated in the locations corresponding to the bone metastases observed in the ¹⁸F-NaF PET/CT: 128 metastases (106 blastic, 22 lytic).

The mean of the SUVmax values was significantly higher in metastases than in degenerative lesions, 26.8±17.3 vs. 15.3±6.3 (P<0.001) and in blastic than in lytic metastases, 27.9±18.3 vs. 22.1±11.3 (P=0.03). A SUVmax value above 42 always represented metastases, with all values above 49 representing blastic metastases. Using the SUVmax values, it was possible to predict the occurrence of metastases (AUC=0.723; P<0.001; 95% CI=0.671-0.776). The mean of the SUVmax with ¹⁸F-NaF was significantly higher in blastic metastases (27.9±18.3 vs. 22.1±11.3, P=0.03), whereas with ¹⁸F-FDG it was significantly higher in lytic ones (3.9±3.4 vs. 9.6±3.3; P<0.01).

SUVmax can contribute to the differentiation of metastases from degenerative lesions, and blastic from lytic metastases.