Zhongguo aizheng zazhi (Sep 2023)

Comparison of 18F-FDG and 68Ga-FAPI PET/CT in the diagnosis of lung metastasis in different malignant tumors

  • YANG Ziyi, GU Bingxin, XU Xiaoping, SONG Shaoli

DOI
https://doi.org/10.19401/j.cnki.1007-3639.2023.09.003
Journal volume & issue
Vol. 33, no. 9
pp. 829 – 833

Abstract

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Background and purpose: 18F-flurodeoxyglucose (18F-FDG) positron emission tomography and computed tomography (PET/CT) is a common method for the diagnosis of malignant tumors with distant metastases. However the detection of lung metastases, especially small lesions, is still unsatisfactory. 68Ga-labeled fibroblast activation protein inhibitors (68Ga-FAPI) have been used to target fibroblast activating proteins and visualize tumor stroma. The diagnostic value of 68Ga-FAPI PET/CT is higher than that of 18F-FDG in the primary sites and metastases of most cancers, but no comparative study has been seen in lung metastases of malignant tumors. Therefore, this study aimed to investigate the diagnostic value of 18F-FDG and 68Ga-FAPI PET/CT in different malignant lung metastases. Methods: The clinical, pathological and imaging data of 20 patients with lung metastasis who underwent 18F-FDG and 68Ga-FAPI PET/CT examination within one week in Fudan University Shanghai Cancer Center from May 2020 to March 2022 were retrospectively analyzed. Among them, 11 cases were epithelial malignant tumors (carcinoma), and 9 cases were mesophyll malignant tumors (sarcoma). The semi-quantitative metabolic parameters including maximum standard uptake value (SUVmax) and target-to-background ratio (TBR) of 68Ga-FAPI and 18F-FDG were compared by paired t test. The linear correlation between SUVmax and TBR and the short diameter of lung metastasis were analyzed. Results: A total of 81 lung metastases (51 carcinomas and 30 sarcomas) were detected in 20 patients, 72 positive lesions were detected by 18F-FDG and 70 positive lesions by 68Ga-FAPI. Compared with 68Ga-FAPI, 18F-FDG uptake was higher in lung metastases, especially those of carcinoma (P<0.001). The results of linear correlation analysis showed that the semi-quantitative metabolic parameters of the two imaging probes were positively correlated with the short diameter of lung metastases (P<0.001). Conclusion: 68Ga-FAPI has no obvious advantage in the detection of lung metastases from malignant tumors. Especially in the diagnosis of lung metastases from epithelial tissues, the uptake of 18F-FDG tends to be higher.

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