What question did this study set out to answer?

The study aims to clarify the diagnostic challenges posed by incidental findings in neuroendocrine tumor imaging.

May 20, 2026Clinical Nuclear Medicine0 citationsOpen Access

Agonist Trap Unmasked

MTMehul TaggarAll India Institute of Medical Sciences Raipur SSShamim A. Shamim RJRonak Jain

Key Points

The study aims to clarify the diagnostic challenges posed by incidental findings in neuroendocrine tumor imaging.
Utilized 68Ga-DOTANOC PET/CT for initial imaging of a neuroendocrine tumor and incidental uterine fibroid.
Followed by a 68Ga-NODAGA-JR11 PET/CT with SSTR antagonist to assess tumor and fibroid uptake.
Analyzed agonists and antagonists' binding characteristics to differentiate between benign and malignant lesions.
68Ga-DOTANOC PET/CT showed uptake in the fibroid, mimicking pelvic metastasis but was confirmed benign via antagonist binding.
Fibroid exhibited no uptake in the 68Ga-NODAGA-JR11 PET/CT, affirming lack of malignant characteristics.
Dual SSTR imaging prevented unnecessary interventions and improved diagnostic certainty in the clinical setting.

Abstract

A 22-year-old woman with a neuroendocrine tumor underwent 68Ga-DOTANOC PET/CT, revealing incidental uterine fibroid uptake mimicking pelvic metastasis. The fibroid's hyperavidity posed diagnostic ambiguity, indistinguishable from low-grade NET deposits. Crucially, subsequent 68Ga-NODAGA-JR11 (SSTR antagonist) PET/CT demonstrated preserved tumor detection but absent fibroid uptake, unequivocally confirming benign leiomyoma. This striking discordance unveils agonists' internalization trap-prolonged DOTANOC retention through SSTR2 endocytosis in estrogen-primed fibroids-versus antagonists' precision: surface binding without non-specific accumulation. In fibroids, the lack of antagonist binding-despite agonist positivity-arises from inadequate receptor density to support sustained surface binding, thereby eliminating false-positive results. Dual SSTR imaging redefines diagnostic certainty, averting interventions while optimizing theranostics.

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