Superiority of ⁶⁸Ga-DOTA-FAPI-04 PET/CT to ¹⁸F-FDG PET/CT in the evaluation of different cancers with bone metastases.

Abstract

⁶⁸Ga-DOTA-FAPI-04 is a new positron imaging agent, and its application in bone metastasis has been limited. The purpose of this retrospective study was to compare the diagnostic ability of ⁶⁸Ga-DOTA-FAPI-04 PET/CT and ¹⁸F-FDG PET/CT to detect bone metastases in patients with different types of cancer. A total of 293 patients with pathologically confirmed primary malignancies were examined with ⁶⁸Ga-DOTA-FAPI-04 PET/CT and ¹⁸F-FDG PET/CT within one week. Using pathological examination or follow-up CT or MRI scan as the gold standard, the diagnostic efficacy of the two methods in differentiating bone metastases was compared (p < 0.05, with statistical significance). The maximum standard uptake value (SUVmax) of the two methods for different types of bone metastasis was further compared. The SUVmax was used to compare the differences between the two methods in detecting bone metastases in different tumor types and different sites. A total of 48 patients were diagnosed with bone metastasis, and 245 patients without bone metastasis. There were 376 bone metastases and 243 benign bone lesions. ⁶⁸Ga-DOTA-FAPI-04 PET/CT and ¹⁸F-FDG PET/CT detected 376 and 228 metastases, respectively. Sensitivity, specificity, positive and negative predictive value (PPV and NPV) and accuracy of ⁶⁸Ga-DOTA-FAPI-04 PET/CT and ¹⁸F-FDG PET/CT were 100.0 % vs 60.6 %, 93.8 % vs 99.2 %, 96.2 % vs 99.2 %, 100.0 % vs 62.0 % and 97.6 % vs 75.8 %, respectively. Compared with ¹⁸F-FDG, ⁶⁸Ga-DOTA-FAPI-04 uptake was significantly increased in both benign bone lesions and metastases (p = 0.001). The uptake of ⁶⁸Ga-DOTA-FAPI-04 for osteoblastic metastasis was also significantly higher than that of ¹⁸F-FDG (p < 0.001). In bone metastasis of lung cancer and gastric cancer, ⁶⁸Ga-DOTA-FAPI-04 uptake was higher than that of ¹⁸F-FDG PET/CT (p < 0.05). Using SUVmax = 4.1 and SUVmax = 6.2 as the cutoff value by ⁶⁸Ga-DOTA-FAPI-04 PET/CT and ¹⁸F-FDG PET/CT, it was possible to predict the occurrence of metastases (AUC = 0.817,95 % CI: 0.791-0.923 vs AUC =0.751,95%CI:0.626-0.875). ⁶⁸Ga-DOTA-FAPI-04 as a novel imaging agent, can detect more bone metastases and has a higher tracer uptake level than ¹⁸F-FDG. Especially for lung and gastric cancer, ⁶⁸Ga-DOTA-FAPI-04 PET/CT may be a more reliable means to detect bone metastases.