Evaluation of unusual neuroendocrine tumours by means of 68Ga-DOTA-NOC PET

Abstract

18F-FDG PET value for the assessment of neuroendocrine tumours (NET) is limited. Preliminary studies indicate that somatostatin receptor PET using 68Ga-DOTA-peptides is more accurate for disease assessment and provide additional data on receptor status, that are crucial for targeted radionuclide therapy. At present, however, few papers investigated the role of 68Ga-DOTA-NOC PET in NET, especially in unusual situations. The purpose of the present study was to evaluate 68Ga-DOTA-NOC for the evaluation of NET of uncommon presentation. Patients with biopsy-proven NET were scheduled for 68Ga-DOTA-NOC PET; we excluded from further evaluation cases with most common NET tumours (gastro-entero-pancreatic and pulmonary localization of primary lesion, MEN syndromes, medullary thyroid carcinoma, pheochromocytomas). PET results were compared with findings of conventional imaging, including CT, ultrasonography, MR and somatostatin receptor scintigraphy; finally PET results were compared with follow-up data with respect to the impact on patient management. Fourteen patients were finally enrolled; primary tumours were located at uterine level (3 cases), prostate (3 cases), ovary (1 case), kidney (1 case), breast (1 case), ear (1 case); also 3 cases of paraganglioma (at neck, abdominal and mediastinum level) and 1 case of lymphoma were included. 68Ga-DOTA-NOC PET was positive, showing at least 1 lesion, in 6/14 cases while 5 cases turned out negative and 2 inconclusive. On a clinical basis, 68Ga-DOTA-NOC provided additional information in comparison to conventional imaging procedures in 7/14 cases, and was considered useful in 12/14 patients, with 8 patients in which 68Ga-DOTA-NOC PET was determinant for patient's management. Although the number of patients studied is limited, our data show that 68Ga-DOTA-NOC can be usefully applied for the evaluation of NET of uncommon presentation; in particular very promising results were obtained in paraganglioma. On the other hand, care has to be paid when studying lesions localized at sites of physiological concentration of the tracer, and in presence of inflammation.