⁶⁸Ga-FAPI PET/CT: Tracer Uptake in 28 Different Kinds of Cancer

Area of Science:

• Nuclear Medicine
• Oncology
• Radiochemistry

Background:

• Fibroblast activation protein (FAP) is overexpressed in cancer-associated fibroblasts across numerous tumor types.
• Quinoline-based fibroblast activation protein inhibitors (FAPIs) are emerging PET tracers with promising results.
• ⁶⁸Ga-FAPI PET/CT offers a novel imaging modality for FAP-expressing tumors.

Purpose of the Study:

• To quantify tumor uptake of ⁶⁸Ga-FAPI PET/CT in diverse primary and metastatic cancers.
• To identify the most promising oncological indications for future ⁶⁸Ga-FAPI PET/CT applications.
• To evaluate the diagnostic performance of ⁶⁸Ga-FAPI PET/CT compared to other imaging techniques.

Main Methods:

• Retrospective analysis of 80 patients with histopathologically proven tumors or unequivocal metastases.
• ⁶⁸Ga-FAPI PET/CT scans performed 1 hour post-injection of 122-312 MBq of ⁶⁸Ga-FAPI-04.
• Tumor uptake quantified using SUV_max and SUV_mean (60% isocontour); tumor-to-background ratios calculated.

Main Results:

• Highest average SUV_max (>12) observed in sarcoma, esophageal, breast, cholangiocarcinoma, and lung cancers.
• Lowest average SUV_max (<6) seen in pheochromocytoma, renal cell, thyroid, adenoid cystic, and gastric cancers.
• Intermediate uptake (SUV 6-12) in hepatocellular, colorectal, head-neck, ovarian, pancreatic, and prostate cancers; excellent tumor-to-background contrast (>3-fold to >6-fold).

Conclusions:

• ⁶⁸Ga-FAPI PET/CT demonstrates high and selective tumor uptake in several prevalent cancer types.
• The tracer shows excellent tumor-to-background contrast due to low uptake in muscle and blood pool.
• ⁶⁸Ga-FAPI PET/CT holds potential for noninvasive tumor characterization, staging, and radioligand therapy.