A case of papillary thyroid carcinoma with Graves ophthalmopathy evaluated by ⁶⁸Ga-FAPI PET/CT

Excerpt

A 56-year-old man was admitted to our hospital with a history of papillary thyroid carcinoma for further ¹³¹I therapy after the total thyroidectomy. ¹³¹I whole-body scan revealed increased NaI activity around thyroid cartilage and cricoid cartilage. Meanwhile, laboratory tests were performed after thyroid hormone withdrawal, showing FT3: 0.71 (reference range, 1.8–3.8 pg/mL), FT4: 0.13 (reference range, 0.8–1.8 ng/dL), TSH: 67.496 (reference range, 0.4–5.5 mIU/L), TgAb < 0.12 (reference range, 0–14.58 IU/mL), TG: 1.05 (reference range, 3.5–77.0 ng/mL) and anti-TSH receptor antibodies (ATSHR): 3.28 (reference range, 0–1.75 IU/L). Subsequently, the patient was enrolled in the clinical trial of ⁶⁸Ga-FAPI PET/CT in solid tumors approved by the institutional review board of our hospital. The maximum intensity projection image revealed increased FAPI uptake in the periorbital areas. On axial images of the periorbital areas, the increased tracer uptake on the PET corresponded to the bilateral thickening extraocular muscles on CT and fusion images (Fig.1). Detailed history-asking revealed that he had proptosis and morning eyelid edema. In addition, he complained of a decrease in visual acuity of the right eye in the last 2 months. These findings suggest the diagnosis of Graves ophthalmopathy. Graves ophthalmopathy (GO) is a chronic inflammatory autoimmune disease which causes inflammation of the extraocular muscles and connective tissue [1]. Inflammation and lymphocytic infiltration of fibroblasts are thought to be caused by the presence of ATSHR [1]. A previous study demonstrated a lack of correlation between ¹⁸F-FDG extraocular muscle uptake and either clinical inflammation score or muscle diameter [1]. ⁶⁸Ga-FAPI is a novel fibroblast activation protein PET agent overexpressed in cancer and inflammation associated fibroblasts [2, 3]. Immune-mediated diseases are associated with substantial activation of tissue resident fibroblasts despite being inflammatory in their nature [2]. Our case showed that ⁶⁸Ga-FAPI might also be valuable in the evaluation of patients with Graves ophthalmopathy. Nevertheless, further research is required to assess the role of ⁶⁸Ga-FAPI PET/CT in the detection, clinical correlation and monitoring of GO.

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