68 Ga-FAPI PET/CT Imaging : Unveiling the Hidden Pitfalls

Area of Science:

• Nuclear Medicine
• Radiochemistry
• Oncologic Imaging

Background:

• Gallium-68 fibroblast activation protein inhibitor (68Ga-FAPI) is a novel positron emission tomography tracer used in oncologic imaging.
• While several pitfalls of 68Ga-FAPI imaging have been documented, a comprehensive understanding is still evolving.
• This case addresses a previously unreported pitfall in 68Ga-FAPI interpretation.

Observation:

• A 69-year-old woman with intrahepatic cholangiocarcinoma underwent 68Ga-FAPI PET/CT after chemoradiotherapy.
• Incidental 68Ga-FAPI uptake was noted in the anorectal sphincter, distinct from the primary tumor.
• Additional non-specific 68Ga-FAPI uptake was observed in the musculoskeletal and gynecological systems.

Findings:

• This is the first reported case of non-specific 68Ga-FAPI expression within the anorectal sphincter.
• The observed uptake in the anorectal sphincter is considered a potential imaging pitfall.
• Non-oncological 68Ga-FAPI uptake can occur in other systems, including musculoskeletal and gynecological.

Implications:

• Awareness of non-specific 68Ga-FAPI uptake in the anorectal sphincter is crucial for accurate oncologic staging and monitoring.
• This finding may necessitate revised interpretation guidelines for 68Ga-FAPI PET/CT scans.
• Further research is warranted to elucidate the biological basis of non-specific 68Ga-FAPI uptake in various tissues.