Clinical Usefulness of ^99mTc-HYNIC-TOC and ¹³¹I-MIBG Scintigraphy in the Evaluation of Adrenal Tumors

Disorders and morphological abnormalities affecting the adrenal gland, could lead to profound clinical consequences, owing to its biochemical structure-activity and morphological characteristics.

The recent focus on theranostic approach has led to a need for tumors characterization and early diagnosis at the molecular level. Many radiotracers have been developed with specific imaging characteristics for the adrenal tumors, by exploiting different physiological mechanisms of uptake and metabolism.

The aim of present study is to provide a prospective confirmation of ¹³¹I-MIBG and ^99mTc-HYNIC-TOC scintigraphy, for the evaluation of patients with known or suspected tumors of the adrenal region.

The research is designed as a cross-sectional observational study of the clinical correlates and diagnostic accuracy of radionuclide-based imaging methods in relation to in vitro analysis, clinical manifestations and morphological characteristics of these tumors. Furthermore, the present study also evaluates the usefulness and the clinical impact of each radiopharmaceutical for the detection and management of tumors, and functional imaging modality as well.

Visual scintigraphic appearance of an increased focal tracer uptake in the suspected tumor site revealed that ^99mTc-HYNIC-TOC is highly sensitive and reliable tumor-seeking radiotracer for adrenal tumors, but does not distinguish between adenoma and pheochromocytoma, and the existence of hormone secreting adrenocortical tumor cells. However, ¹³¹IMIBG scintigraphy is highly sensitive and specific method only in differentiating catecholamine-secreting adrenal tumors.

Clinical significance of this research is in the accurate localization of adrenal tumors, and is of paramount importance for an algorithmic diagnostic approach and management, and provide the rationale to different therapeutic possibilities.