Evaluation of fibroinflammatory activity in thyroid eye disease using [¹⁸F]AlF-NOTA-FAPI-04 PET/CT: A prospective...

Area of Science:

• Nuclear medicine imaging
• Ophthalmology
• Radiopharmaceuticals

Background:

• Thyroid eye disease (TED) is an autoimmune condition affecting the tissues around the eye.
• Accurate assessment of TED disease activity is crucial for timely and effective treatment.
• Current methods like the Clinical Activity Score (CAS) have limitations in fully capturing disease activity.

Purpose of the Study:

• To evaluate the diagnostic value of [¹⁸F]AlF-NOTA-FAPI-04 positron emission tomography/computed tomography (PET/CT) in assessing the disease activity of TED.
• To compare the efficacy of [¹⁸F]AlF-NOTA-FAPI-04 PET/CT with the established CAS for TED activity assessment.

Main Methods:

• Prospective recruitment of 23 TED patients and 10 healthy controls for [¹⁸F]AlF-NOTA-FAPI-04 PET/CT scans.
• Classification of TED eyes as active (CAS+) or inactive (CAS-) based on the Clinical Activity Score.
• Qualitative and quantitative PET analysis of extraocular muscles (EOMs), including SUVmax and target-to-background ratio (TBR).
• Pathological assessment of EOM samples as a gold standard to validate PET and CAS findings.

Main Results:

• Diffuse high [¹⁸F]AlF-NOTA-FAPI-04 uptake and excellent TBR were observed in pathologically active EOMs.
• Active EOMs showed significantly higher SUVmax and TBR compared to inactive EOMs and control eyes (P < .001).
• An SUVmax cutoff of 5.95 demonstrated high accuracy (AUC = 0.98) for predicting active TED.
• [¹⁸F]AlF-NOTA-FAPI-04 PET/CT achieved 100% sensitivity and specificity, outperforming CAS (72.7% sensitivity).
• SUVmax positively correlated with pathological fibroinflammatory scores (r=0.68, P=.004).

Conclusions:

• Diffuse high FAPI uptake in EOMs reflects TED activity and correlates with pathological findings.
• [¹⁸F]AlF-NOTA-FAPI-04 PET/CT is a promising, reliable, non-invasive tool for assessing TED disease activity.
• This PET/CT approach may offer superior diagnostic accuracy compared to the CAS for evaluating TED activity.