Increased ¹⁸F-FAPI uptake in bones and joints of lung cancer patients: characteristics and distributions

Objective: This study investigated the distribution and characteristics of various bone and joint lesions on ¹⁸F-FAPI PET/CT in lung cancer patients.

Methods: Seventy-four lung cancer patients who underwent ¹⁸F-FAPI PET/CT were reviewed. Bone and joint lesions with elevated ¹⁸F-FAPI uptake were recorded and analyzed. The distribution and maximum uptake value (SUV_max) of different benign lesions or bone metastases were presented. In addition, the SUV_max of bone metastases on ¹⁸F-FDG and ¹⁸F-FAPI-04 PET/CT were also compared.

Results: In 53 patients, a total of 262 lesions presented ¹⁸F-FAPI accumulation. Bone metastases were mainly in vertebrae, pelvis, and ribs, while benign lesions were in vertebral margins, alveolar bone, and shoulder joints. The SUV_max of bone metastases was significantly higher than that of benign lesions ([Formula: see text] vs. [Formula: see text], [Formula: see text]), with NSCLC cases having higher SUV_max values than SCLC cases ([Formula: see text] vs. [Formula: see text], [Formula: see text]). Among benign lesions, arthritis and periodontitis demonstrated higher SUV_max than degenerative lesions (arthritis: [Formula: see text]; periodontitis: [Formula: see text]; degenerative diseases: [Formula: see text]; [Formula: see text] and [Formula: see text], respectively). The SUV_max of bone metastases was comparable between ¹⁸F-FDG and ¹⁸F-FAPI PET/CT. However, ¹⁸F-FAPI PET/CT was found to be superior in identifying cranial metastases compared to ¹⁸F-FDG PET/CT (TBR_met/brain: [Formula: see text] vs. [Formula: see text], [Formula: see text]).

Conclusion: This study demonstrated that ¹⁸F-FAPI PET/CT is a valuable imaging modality for detecting bone and joint lesions in lung cancer patients. The SUV_max of malignant lesions was higher than that of benign lesions, but cannot accurately distinguish benign and malignant lesions. The uptake of FAPI differs among lesions with different pathological types.