Highly variable biodistribution of Ga labeled somatostatin analogues Ga-DOTA-NOC and Ga-DOTA-TATE in neuroendocrine tumors: clinical implications for somatostatin receptor directed PET/CT.

BACKGROUND

Somatostatin receptor (SSTR)-targeted positron emission tomography/computed tomography (PET/CT) imaging has risen to the forefront for neuroendocrine tumor (NET) detection and management, yet the variability of significant uptake variability (SUV) as a semiquantitative measure of disease detection and tumor response to treatment has not been fully explored.

METHODS

We assess the reproducibility and interscan variability of SUV metrics of normal tissue and NET in serial Ga-DOTA-NOC and Ga-DOTA-TATE PET imaging to clinically monitor disease state. Eighty-one patients were enrolled in this retrospective study.

RESULTS

Both primary and metastatic hepatic lesions demonstrated SUV (SUV 16.5±8.0). The median SUV was 16 for the spleen, 9.7 for the pituitary, 12.6 for the adrenal glands, and 4.8 for the liver. The normal pituitary gland demonstrates focal homogenous uptake with SUV range of 4.5-23. The adrenal gland showed uptake with SUV range of 4.1-29.4, which is more than two times greater than liver uptake (SUV range, 2.3-12.4). Highest physiological uptake seen in the spleen (average SUV of 17.3, range of 5.4-34.4).

CONCLUSIONS

The highly variable nature of regional SUV and SUV in both physiologic tissue and lesions suggests the need for incorporation of more reliable quantitative measures for clinical decision making.