Investigating the diffuse pancreatic expression of [68Ga]Ga-DOTA-FAPI: location, timing, and molecular imaging approaches

First Clinical Experience of 68Ga-FAPI PET/CT in Tertiary Cancer Center: Identifying Pearls and Pitfalls

Background/Objectives: Over the past four years, 68Ga-fibroblast activation protein inhibitor (FAPI) positron emission tomography/computed tomography (PET/CT) has been established at a tertiary cancer care facility in Jordan. This retrospective study aims to explore tracer uptake metrics across various epithelial neoplasms, identify diagnostic pitfalls associated with 68Ga-FAPI PET/CT, and evaluate the influence of 68Ga-FAPI PET/CT staging results on changes in therapeutic intent compared to gold standard molecular imaging modalities. Methods: A total of 48 patients with biopsy-confirmed solid tumors underwent 77 68Ga-FAPI PET/CT examinations for molecular imaging assessment, encompassing neoplasms originating from the gastrointestinal tract, head and neck, hepatobiliary system, pancreas, breast, and lung. Results: Notably, pancreaticobiliary tumors exhibited the highest tracer uptake, with mean maximum standardized uptake values (SUVmax) and tumor-to-background ratios (TBR) surpassing 10. A comparative sub-analysis of 68Ga-FAPI PET metrics in 20 treatment-naïve patients revealed a significant correlation between 68Ga-FAPI uptake metrics and tumor grade (Spearman's rho 0.83; p = 0.00001). Importantly, the results from 68Ga-FAPI PET/CT influenced treatment decisions in 35.5% of the cases, primarily resulting in an escalation of management plans. A total of 220 diagnostic challenges were identified across 88.3% of the scans, predominantly within the musculoskeletal system, attributed to degenerative changes (99 observations). Conclusions: This comprehensive analysis highlights the potential significance of 68Ga-FAPI PET/CT in oncological imaging and treatment strategy, while also emphasizing the necessity for meticulous interpretation to mitigate diagnostic challenges.

Incidental Intense Fibroblast Activation Protein Inhibitor (FAPI) Uptake in Bilateral Gluteal Myositis Ossificans: A Case Report

Positron emission tomography/computed tomography (PET/CT) using 18F-fluorodeoxyglucose ([18F]-FDG) is a widely adopted imaging modality for detecting hypermetabolic lesions. However, emerging positron-emitting tracers, such as radiopharmaceuticals featuring fibroblast activation protein (FAP) inhibitors (FAPI) labeled with [18F] or [68Ga], have opened new avenues in nuclear medicine. This case report focuses on the unique behavior of [68Ga]-FAPI in bilateral gluteal myositis ossificans, an infrequent condition characterized by soft tissue ossification. A 45-year-old woman with gastric adenocarcinoma underwent subtotal gastrectomy and received neoadjuvant and adjuvant chemotherapy; [68Ga]-FAPI PET revealed metastatic processes and unexpected [68Ga]-FAPI avid intramuscular ossifications in the pelvic and bilateral thigh muscles. Even though there was no history of trauma, the patient was diagnosed with myositis ossificans, a condition marked by non-cancerous ectopic ossifications. Diagnosis relies on history, radiology, and/or histology. FAPI imaging, increasingly used for inflammatory and infectious diseases, can exhibit uptake in benign conditions, including those involving bones and joints. This case report is the first to document incidental bilateral [68Ga]-FAPI uptake in bilateral gluteal myositis ossificans. The robust [68Ga]-FAPI activity in myositis ossificans highlights the importance of considering myositis ossificans in the context of soft tissue calcifications with intense [68Ga]-FAPI uptake.