Increased 68Ga-FAPI Uptake in the Pulmonary Cryptococcus and the Postradiotherapy Inflammation

Area of Science:

• Oncologic imaging
• Nuclear medicine
• Radiopharmaceuticals

Background:

• Nasopharyngeal carcinoma (NPC) recurrence detection is crucial for patient management.
• 18F-FDG PET/CT is a standard imaging modality for NPC.
• 68Ga-FAPI PET/CT is an emerging PET tracer targeting cancer-associated fibroblasts.

Observation:

• A patient with a history of NPC presented with a new pulmonary nodule.
• Both 18F-FDG and 68Ga-FAPI PET/CT demonstrated intense uptake in the pulmonary nodule.
• 68Ga-FAPI PET/CT also showed increased uptake in the nasopharynx.

Findings:

• CT-guided biopsy revealed the pulmonary nodule to be cryptococcus, a fungal infection.
• The increased 68Ga-FAPI uptake in the nasopharynx was deemed a false-positive finding.
• Stable Epstein-Barr virus levels and lack of progression on follow-up imaging supported the false-positive interpretation.

Implications:

• 68Ga-FAPI PET/CT shows potential for detecting NPC recurrence but requires careful interpretation due to possible false positives.
• Distinguishing between true tumor recurrence and benign findings like fungal infections is critical.
• Further studies are needed to define the specificity of 68Ga-FAPI in NPC follow-up.