Combination of 68Ga-DOTA-TATE and 18F-FDG PET/CT in evaluation of pituitary tumor and the remaining adenohypophysis: A proof of concept study

Objectives This study was designed to investigate the combination of 18F-FDG and 68Ga-DOTA-TATE PET/CT in differentiation of sella region tumors and evaluation of the remaining adenohypophysis.

Methods Thirty patients (F21, M 9, 6-70 y) in suspicion of sellar region tumor were recruited. All patients underwent both 68Ga-DOTA-TATE and 18F-FDG PET/CT of the brain within one week. According to the pathology and follow-ups, 28 patients were diagnosed with pituitary adenoma, including two with apoplexy and one accompanied with a Rathke’s cleft cyst. The other two patients had pituitary abscess and lymphocytic hypophysitis, respectively. In 13 patients with pituitary function tests, 9 showed hypofunction at least in one test and 4 were in normal range. The two groups were compared of the maximum standardized uptake values (SUVmax) of 68Ga-DOTA-TATE in the remaining pituitary tissue.

Results In the 28 patients , adenoma it showed high uptake of 18F-FDG (SUVmax 3.5-17.4) and moderate to high uptake of 68Ga-DOTA-TATE (SUVmax 2.2-10.0). The normal pituitary tissue showed minimal uptake of 18F-FDG (SUVmax 0.7-2.2) and moderate to high uptake of 68Ga-DOTA-TATE. There was significant difference of SUVmax between the patients with hypo- and normal function of adenohypophysis (P<0.01). Inflammatory tissue showed moderate uptake of 18F-FDG (SUVmax 1.7-3.5) but minimal accumulation of 68Ga-DOTA-TATE (SUVmax 1.2-2.6). Neither cyst, pus, nor necrosis showed uptake of both tracers. Lymphocytic hypophysitis showed symmetric enlargement of the pituitary with moderate uptake of 18F-FDG and homogenous decrease of 68Ga-DOTA-TATE uptake.

Conclusions Combining analysis of 68Ga-DOTA-TATE and 18F-FDG PET/CT is helpful for differentiation of sellar region tumors and in evaluation of the remaining adenohypophysis, especially when referring to the patients’ history, pituitary functional tests, and MRI.