Increased uptake of 68Ga-DOTA-FAPI-04 in bones and joints: metastases and beyond

Abstract

Purpose: To describe the uptake of 68 Gallium-labelled broblast activation protein inhibitor ( 68 Ga-FAPI) in bones and joints for better understanding of the role of 68 Ga-FAPI PET in benign and malignant bone lesions and joint diseases.Methods: All 129 68 Ga-FAPI PET/MR or PET/CT scans from June 1, 2020 to February 20, 2021 performed at our PET centre were retrospectively reviewed. Foci of elevated 68 Ga-FAPI uptake in bones and joints were identi ed. All lesions were divided into malignant and benign disease. Benign lesions included osteo brous dysplasia, periodontitis, degenerative bone diseases, arthritis, and other in ammatory or trauma-related abnormalities. The number, locations and SUVmax of all lesions were recorded and analysed.Results: Elevated uptake of 68 Ga-FAPI in/around bones and joints were found in 82 cases (63.57%). A total of 295 lesions were identi ed, including 94 (31.9%) malignant lesions (all were metastases) and 201 (68.1%) benign lesions. The benign lesions consisted of 13 osteo brous dysplasia, 48 degenerative bone disease, 33 periodontitis, 56 arthritis, and 51 other in ammatory or trauma-related abnormalities. Spine, shoulder joint, alveolar ridge, and pelvis were the most commonly involved locations. Bone metastases were mainly distributed in the spine, pelvis and ribs. Among benign diseases, periodontitis and arthritis are site-speci c. The mean SUVmax of bone metastases was signi cantly higher than that of benign diseases (7.14 ± 4.33 vs. 3.57 ± 1.60, p < 0.0001), but overlap existed. The differences in SUVmax among subgroups of benign diseases were statistically signi cant (p < 0.0001), with much higher uptake in periodontitis (4.45 ± 1.17). Conclusion: 68Ga-FAPI accumulated in both bone metastases and some benign diseases of bones and joints. Although the uptake of 68 Ga-FAPI was often higher in bone metastases, this nding cannot be used to distinguish between benign and malignant lesions.

Head-to-head evaluation of [18F]FDG and [68 Ga]Ga-DOTA-FAPI-04 PET/CT in recurrent soft tissue sarcoma

“…This is caused by fibrotic activity in these conditions [ 26 ]. Thus, more researches focused on non-tumor–specific uptake of FAPI are still needed [ 27 , 28 ].…”

Validating Cell Surface Proteases as Drug Targets for Cancer Therapy: What Do We Know, and Where Do We Go?

“…Based on their selective and strong binding to FAP, a multitude of radiolabeled FAP inhibitors (FAPI) have been generated and are now widely used in experimental tumour diagnosis (reviewed in [10,14]). Several FAPI tracers recently entered the clinical phase for pan-tumour imaging, diagnosis, and staging examinations (Table S1) [121]. To turn the FAPI radiopharmaceuticals into theranostics, the linker region was modified to obtain improved tumour retention and to allow the use of radionuclides suited for therapy [122].…”

Emerging Role of FAPI PET Imaging for the Assessment of Benign Bone and Joint Diseases

“…In this scenario, a recent article compared the radiolabeled FAPI uptake in bones and joints between malign and benign lesions (such as periodontitis, osteofibrous dysplasia, degenerative bone disease, arthritis and trauma related lesions) [ 21 ]. The authors reported that, even if overlap occurred in some cases, maximum standardized uptake value (SUV max ) of bone metastases was significantly higher compared to benign lesions, even if no significant differences in terms of uptake between such benign lesions was reported, with the exception of periodontitis.…”