SUN-LB076 Potential Role of Gallium-68-Peptides and Fluorine-18-FDG PET/CT and Ki67 in Patients with Post-Surgical Residual Pituitary Adenoma

Purpose: Pituitary adenomas are in most of cases benign lesions. However, in around 25% of cases they can show aggressive behavior, such invasiveness of pituitary region surrounding structures, progressive or rapid increase in size or evolvement in pituitary carcinoma. In recent years, 68Ga-peptides and 18F-FDG PET/CT have been applied in the functional assessment of residual pituitary adenomas. Methods: We retrospectively reviewed our series of patients submitted to 68Ga-peptides and/or 18F-FDG PET-CT for evaluating residual pituitary adenomas after primary surgery. Results: Sixteen patients underwent 68Ga-peptides and/or 18F-FDG PET/CT in the period 2012-2018 at our Institution. A total of 15 68Ga-peptides PET/CT scans and 8 18F-FDG PET/CT scans were performed. Fourteen patients had pituitary adenoma, and two pituitary carcinoma. Nine patients were affected by not-secreting (null cell) pituitary adenoma; 3 patients by Cushing disease; 3 patients by acromegaly and a single patients by prolactinoma. All patients underwent partial removal of the pituitary adenoma, as all cases invaded the cavernous sinus. Mean Ki67 was 4% (SD: 3). Positivity at 68Ga-peptides PET/CT was detected in 10 patients. Positivity at 18F-FDG PET/CT was detected in 6 patients. Six patients were submitted to both PET/CT scans: 4 showed concordant results and two were positive only at 68Ga-peptide PET/CT. Nine patients with residual tumor positive at 68Ga-peptides PET/CT were treated with long-acting somatostatin analogues (L-SSA). Progression of the residual adenoma was observed in 9 patients: 6 were positive at 68Ga-peptide PET/CT and 5 were positive at FDG PET/CT. 5 patients were on treatment with L-SSA. Mean follow-up was 37.8 months (DS:30). The only determinant of progression disease was the Ki67: in patients with progression of pituitary adenoma, mean Ki67 was 5% (SD: 3, p=0.05) and in patients with stable disease its mean value was 1.5% (SD:1.5). Conclusion: 68Ga-peptides and 18F-FDG PET/CT can be useful for functional evaluation of residual pituitary adenomas after primary surgery and in scheduling the therapeutic management. In any case, the main determinant of disease progression is represented by the Ki67 index. Unless otherwise noted, all abstracts presented at ENDO are embargoed until the date and time of presentation. For oral presentations, the abstracts are embargoed until the session begins. Abstracts presented at a news conference are embargoed until the date and time of the news conference. The Endocrine Society reserves the right to lift the embargo on specific abstracts that are selected for promotion prior to or during ENDO.