Liver metastases from medullary thyroid carcinoma detected on ⁶⁸Ga-FAPI-04 PET/CT

Excerpt

Herein we present a 38-year-old woman with a 10-year history of metastatic medullary thyroid carcinoma, with highly elevated calcitonin levels (from 36,000 to 96,800 ng/l) during follow-up after receiving four cycles ¹⁷⁷Lu-DOTATATE. The patient underwent ⁶⁸Ga-DOTATATE PET/CT as part of a screening procedure since the patient has always been FDG-negative during the course of the disease. Multiple metastatic bone lesions and mediastinal lymph nodes overexpressing somatostatin receptors (SSTR) suggested stable disease on ⁶⁸Ga-DOTATATE PET/CT (Fig. 1A). However, heterogeneous uptake in the liver was suspicious for new metastases, and the patient underwent PET imaging (Fig. 1B) with ⁶⁸Ga-labelled fibroblast activation protein (FAP) inhibitor (⁶⁸Ga-FAPI-04) for further evaluation. All SSTR-positive lesions demonstrated FAP expression with a higher tumour-to-background ratio (Fig. 1C, D), except one SSTR-positive (Fig. 1E) metastatic bone lesion, which was ⁶⁸Ga-FAPI-04 negative (Fig. 1F). However, ⁶⁸Ga-FAPI-04 PET/CT revealed multiple metastatic liver lesions that ⁶⁸Ga-DOTATATE PET/CT failed to detect (Fig. 1G–J). …