Prognostic significance of 68Ga-FAPI-PET/CT in patients with bone metastases in various cancers

Abstract

Objective:This study aimed to compare and18FDGPET/CT in patients who develop bone metastases due to various cancers and to investigate the prognostic significance of the 68FAPI-PET/CT SUVmax value for survival. Methods:Patients with bone metastases who underwent both 68Ga-FAPI PET/CTand18FDGPET/CT within a 1-week period were included in this retrospective study. The effect of the SUVmax value of bone lesions on overall survival was analyzed. Results:A total of 75 eligible patients with 139 bone lesions were included in this study. The median age of the patients was 55(30–83) and 48 patients (64%) were newly diagnosed. The primary lesion median 68Ga-FAPI PET/CT SUVmax value was higher than the median 18FDGPET/CT SUVmax (10.75 versus 6.7). Bone lesions 68Ga-FAPI PET/CT SUVmax median(IQR) were 7.8(4.6–13.2), and 18FDGPET/CT SUVmax of bone lesions were 5.9(3.8–8.2). More bone lesions were detected on 68Ga-FAPI PET/CT than on 18FDGPET/CT(median IQR 4 [1–9] versus 2 [1–6](p=0.014). The extra lesions observed on 68Ga-FAPI PET/CT were mostly sclerotic bone lesions(p = 0.001).68Ga-FAPI PET/CT SUVmax was significantly higher in vertebra and thorax lesions(p=0.011 and p=0.018, respectively). While the bone lesion 68Ga-FAPI PET/CT SUVmax affected the OS, the 18FDGPET/CT SUVmax value did not affect the OS (p<0.001 and p=0.079, respectively). In ROC analysis, a cut-off value of 68Ga-FAPI PET/CT SUVmax >7.7 was found for OS(AUC:0.619). The median OS in the group above the cut-off value was worse than that in the group below the cut-off value (32 versus 45) months (p=0.002). In the multivariate analysis for OS, the 68Ga-FAPI PET/CT SUVmax of bone lesions was an important parameter,as well as cancer subtype, ALP level, and disease occurrence. Conclusions:68Ga-FAPI PET/CT detected more bone lesions and higher SUVmax values than 18FDGPET/CT in various cancers. The prognostic value of the SUVmax value of 68Ga-FAPI PET/CT bone lesions was observed regardless of disease subtype.