Lower 68 Ga‐DOTATOC uptake in nonfunctioning pituitary neuroendocrine tumours compared to normal pituitary gland—A proof‐of‐concept study
Axel Tjörnstrand, Olivera Casar‐Borota, Kerstin Heurling, Michael Schöll, Peter Gjertsson, Jakob Himmelman, Oleksiy Itsenko, Oskar Ragnarsson, Helena Filipsson Nyström
Source abstract
Abstract Objectives 68 Ga‐ DOTATOC PET targets somatostatin receptors ( SSTR s) and is well established for the detection of SSTR ‐expressing tumors, such as gastrointestinal neuroendocrine tumors. Pituitary adenomas, recently designated as pituitary neuroendocrine tumors (Pit NET s), also express SSTR s, but there has been no previous evaluations of 68 Ga‐ DOTATOC PET in Pit NET patients. The aim of this pilot study was to evaluate the diagnostic properties of 68 Ga‐ DOTATOC PET in the most common Pit NET , ie non‐functioning ( NF )‐Pit NET . Design/Patients NF ‐Pit NET patients (n = 9) and controls (n = 13) were examined preoperatively with 68 Ga‐ DOTATOC PET for 45 min after tracer injection in dynamic list mode. Tumor specimens were collected during surgery in patients. MRI and PET images were co‐registered using PMOD software. The maximum standard uptake value ( SUV max ) was analyzed in manually outlined regions of interest ( ROI ) around the tumor in patients and around the pituitary gland in controls. Immunohistochemical analyses were conducted on tumor specimens for assessment of tumor cell type and SSTR expression. Results Median SUV max ( IQR ) was lower in patients than in controls (3.9 [3.4‐8.5] vs 14.1 [12.5‐15.9]; P < .01]. In ROC analysis, the area under the curve was 0.87 ( P < .01) for SUV max , with 78% sensitivity and 92% specificity. Immunohistochemical analysis showed NF ‐Pit NET s were of gonadotroph (n = 7) and corticotroph (n = 2) origin. SSTR expression was high for SSTR 3, low‐to‐moderate for SSTR 2, and low for SSTR 1 and SSTR 5. Conclusions This proof‐of‐concept study shows that 68 Ga‐ DOTATOC PET can be used to differentiate between normal pituitary tissue and NF ‐Pit NET .
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