⁶⁸Ga-DOTANOC PET/CT in the baseline evaluation of patients with Multiple Endocrine Neoplasia (MEN) syndromes

Objectives: Multiple Endocrine Neoplasia (MEN) comprises several distinct syndromes, constituting endocrine tumors as well as several non-endocrine pathologies. MEN 1 (MEN 1 gene mutation) primarily constitutes multi-gland parathyroid disease, pituitary adenoma and pancreatic tumors. MEN 2A (RET gene mutation) comprises of medullary thyroid carcinoma, pheochromocytoma and multi-gland parathyroid disease, while MEN 2B (RET gene mutation), additionally has mucosal neuromas. Multiple individual imaging modalities such as endoscopic ultrasound, neck ultrasound, CT, MRI, Sestamibi scan are utilized to detect individual tumors in patients with MEN syndromes. The aim of the present study was to assess the diagnostic performance of ⁶⁸Ga-DOTANOC PET/CT in patients with genetic mutation confirmed MEN syndromes.

Methods: Records of 181 patients with MEN syndromes who had undergone ⁶⁸Ga-DOTANOC PET/CT from January, 2017 to July, 2019 were retrospectively reviewed. Of these, 76 patients (mean age: 35.7 years; 40 men, 36 women) had undergone the PET/CT study prior to any therapy initiation and had genetic mutation analysis confirming MEN syndrome. The PET/CT study was interpreted independently by two experienced Nuclear Medicine physicians and any pathologic uptake was assessed semi-quantitatively using Standardized uptake maximum (SUVmax) values. Histopathology details were also reviewed for the patients who underwent surgery. Findings of other conventional imaging were utilized for correlation, especially in lesions without histopathologic confirmation.

Results: Patients with MEN 1 formed the majority of the study candidates (69/76) followed by MEN 2A (5/76) and MEN 2B (2/76). ⁶⁸Ga-DOTANOC PET/CT detected a total of 102 lesions corresponding to primary tumors in the MEN syndromes. Maximum lesions (n=47) were detected in the pancreas (mean SUVmax 38.9±22.4), all of which were consistent with neuroendocrine tumor (NET; confirmation with histopathology in 38, correlative imaging in 9). 4 lesions were detected in the adrenals, consistent with pheochromocytoma. 22 parathyroid lesions (multi-gland disease), 4 thyroidal lesions (Medullary thyroid cancer) and 25 pituitary lesions (pituitary adenoma) were also detected. Metastatic sites were detected in 12/76 (12.7%) patients. Overall, the highest detection rate was for pancreatic NETs (68.1%) followed by pituitary adenomas (36.2%) in patients with MEN 1.

Conclusions: Somatostatin receptor imaging using ⁶⁸Ga-DOTANOC PET/CT can be a useful initial diagnostic modality for evaluation of patients with clinical suspicion of MEN syndromes. Lesions detected on PET/CT can then be further evaluated using correlative imaging and/ or histopathologic analysis. Further, a baseline study can be utilized for assessing response to treatment, later during the course of management.