Pre- and postoperative 68 Ga-DOTATOC positron emission tomography for hormone-secreting pituitary neuroendocrine tumors.

Tjörnstrand, Axel; Casar-Borota, Olivera; Heurling, Kerstin; Schöll, Michael; Gjertsson, Peter; Ragnarsson, Oskar; Filipsson Nyström, Helena

OBJECTIVES Somatostatin receptors (SSTRs) are potential targets for detecting pituitary neuroendocrine tumors (PitNETs) that can be visualized effectively with 68 Ga-labeled PET tracers. With this study, we have evaluated the diagnostic properties of such a tracer, 68 Ga-DOTATOC, in patients with hormone-producing PitNETs before and after surgery. DESIGN /Methods This prospective case-control study presents preoperative positron emission tomography (PET) and histopathological data in 18 patients with somatotroph (n = 8), corticotroph (n = 7), and thyrotroph (n = 3) PitNETs. Patients were scanned pre- and postoperatively with 68 Ga-DOTATOC PET. For the postoperative part of the study, patients with gonadotroph tumors (n = 7) were also included. Fifteen pituitary healthy controls underwent the same protocol once. The maximum standard uptake value (SUVmax ) was analyzed in manually outlined regions around the tumor in patients and around the pituitary gland in controls. Tumor specimens were collected during surgery in subjects for assessment of adenohypophyseal tumor cell type and the SSTR expression. RESULTS Thyrotroph tumors showed higher uptake (median SUVmax 41.1; IQR 37.4-60.0) and corticotroph tumors lower uptake (SUVmax 6.8; 2.6-9.3) than normal pituitary gland (SUVmax 13.8; 12.1-15.5). The uptake in somatotroph tumors (SUVmax 15.9; 11.6-19.7) was similar to the uptake in the pituitary gland. There was a strong correlation between SUVmax and SSTR2 expression (r = 0.75 (P < .01)). In the postoperative evaluation, PET was able to correlate tracer uptake with biochemical cure and non-cure in patients with an abnormal postoperative magnetic resonance image and a preoperative tumor uptake SUVmax >13.8. CONCLUSIONS 68 Ga-DOTATOC PET can be used to detect thyrotroph tumors in the pre- and postoperative imaging assessment. Corticotroph tumors had a significantly lower uptake compared to the pituitary gland but without a distinct increased tumor uptake the clinical postoperative value is limited.