FAP-Imaging in Rare Cancer Entities - First Clinical Experience in a Broad Spectrum of Malignancies

Abstract

Purpose: 68Ga-FAPI (fibroblast activation protein inhibitor) is a rapidly evolving and highly promising radiotracer for PET/CT imaging, presenting excellent results in a variety of tumor entities, particularly in epithelial carcinomas. This retrospective analysis sought to evaluate the potential and impact of FAPI-PET/CT in rare cancer diseases with respect to improvement in staging and therapy, based on tracer uptake in normal organs and tumors.Material and Methods: 55 patients with rare tumor entities, defined by a prevalence of 1 person out of 2000 or less, received a 68Ga-FAPI-PET/CT scan. 14 women and 41 men (median age 60) were included within the following subgroups: cancer of unknown primary (n=10), head-and-neck-cancer (n=13), gastro-intestinal and biliary-pancreatic cancer (n=17), urinary tract cancer (n=4), neuroendocrine cancer (n=4) and others (n=7). Tracer uptake was quantified by standardized uptake values SUVmax and SUVmean and the tumor-to-background ratio (TBR) was determined (SUVmax tumor/ SUVmean organ). Results: In 20 out of 55 patients the primary tumor was identified and 31 patients presented metastases (n=88), characterized by a high mean SUVmax in primary (10.1) and metastatic lesions (7.6). Highest uptake was observed by liver metastases (n=6) with a mean SUVmax of 9.8 and a high TBR of 8.7, closely followed by peritoneal carcinomatosis (n=16) presenting a mean SUVmax of 9.8 and an excellent TBR of 29.6. In terms of the included subgroups the highest uptake regarding mean SUVmax was determined in gastro-intestinal and biliary-pancreatic cancer with 9.8 followed closely by urinary tract cancer with 9.5 and head-and-neck cancer (9.1). Conclusion Due to excellent tumor visualization and, thereby, sharp contrasts in terms of high TBRs in primary and metastatic lesions in different rare malignancies, 68Ga-FAPI-PET/CT crystallizes as a powerful and valuable imaging tool, particularly with respect to epithelial carcinomas, and therefore an enhancement to standard diagnostics imaging methodologies. The realization of further and prospective studies is of large importance to confirm the potential of FAP-imaging in oncology.

FAP and FAPI-PET/CT in Malignant and Non-Malignant Diseases: A Perfect Symbiosis?

“…The overexpression of FAP in many malignancies is now well-known. Therefore, FAPI-PET/CT is a highly promising imaging method in a variety of malignancies [ 78 , 79 , 80 ] ( Figure 4 ). The exact role of FAP in a tumorigenesis is unknown; however, its expression is related to the tumor proliferation, migration and invasion [ 46 ].…”

Physiological tracer distribution and benign lesion incidental uptake of Al18F-NOTA-FAPI-04 on PET/CT imaging

“…Previous studies have demonstrated that FAPI PET/computed tomography (CT) performs well in cases of epithelial tumors, including those in the breasts, pancreas, and gastrointestinal tract, because of their excellent tumor uptake and high sensitivity for detecting lesions [6][7][8][9][10][11]. Other types of cancer, such as sarcomas and lymphomas, have also been well imaged using FAPI PET/CT [12][13][14][15][16][17]. Therefore, FAPIs may emerge as promising alternatives to fluorodeoxyglucose (FDG) for tumor imaging, and it has even been proposed that FAPI PET/CT might replace FDG PET/CT in the next decade [2].…”

The application of FAPI-targeted theranostics in pancreatic cancer: a narrative review

“…68 Ga-FAPI PET/CT exhibits high sensitivity in targeting pancreatic cancer and present good image contrast. [46,47] Although the mean SUVmax of 68 Ga-FAPI is slightly higher or almost the same as 18 F-FDG, 68 Ga-FAPI displays a significantly higher tumor-to-background ratio (TBR) and sharp contrasts due to the low background uptake (Fig. 1).…”

“…Precise evaluation of disease is crucial for understanding the stage in pancreatic cancer patients for optimizing therapeutic [43] 68 Ga FAPI-04 Imaging PET/CT Case report Human 1 Zhao et al [44] 68 Ga FAPI-04 Imaging PET/CT Case report Human 1 Luo et al [45] 68 Ga FAPI-04 Imaging PET/CT Case report Human 1 Dendl et al [46] 68 Ga FAPI-04 FAPI-46 FAPI-73…”