False-positive [ 68 Ga]Ga-FAPI-04 PET/CT Following Treatment of 177 Lu-DOTATATE PRRT in a Patient With Metastatic High-grade Well-differentiated Neuroendocrine Tumor.

Parghane, Rahul Vithalrao; Yadav, Subhash; Saju, Austin; Basu, Sandip · Clin Nucl Med · 2026

case_report · Level V

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Abstract

We present a high-grade well-differentiated NET with large lesions that demonstrated both SSTR and [ 18 F]F-FDG avidity on baseline PET/CT, an outstanding response following 177 Lu-DOTATATE-PRRT with complete resolution of SSTR and [ 18 F]F-FDG uptake, and significant size reduction of liver lesions. Non-SSTR and non-[ 18 F]F-FDG-avid change was noted in segment V, demonstrated uptake on [ 68 Ga]Ga-FAPI-04 PET/CT, and confirmed as fibrotic changes post-PRRT. Following PRRT, analysis of [ 68 Ga]Ga-FAPI-04 PET/CT in well-differentiated NET is important to avoid misinterpretation. Benign fibrosis following treatment may show FAPI uptake as a possible source of false-positive findings on [ 68 Ga]Ga-FAPI-04 PET/CT in the evaluation of NET.

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