EANM position on positron emission tomography in suspected functional pituitary neuroendocrine tumours

Excerpt

Pituitary neuroendocrine tumours (PitNET) [1] are, after meningioma, the most frequent intracranial tumours. They are classified according to their size (micro < 10 mm, macro ≥ 10 mm and giant ≥ 40 mm), their hormonal secretion pattern and molecular expression profile. Although most PitNET are benign, they can cause significant morbidity due to local compression and associated hormonal syndromes. Clinical management is multidisciplinary, and treatment consists of surgical resection, radiotherapy, pharmacotherapy or a combination. Magnetic resonance imaging (MRI) is the primary diagnostic method, and dedicated protocols include dynamic contrast-enhanced imaging [2]. Ultra-high field MRI (7T) has shown to increase detection, particularly in small micro-PitNET [3]. However, there remain some unmet diagnostic needs. Some functional micro-PitNET (including 30–40% of corticotroph adenomas) are not readily visualized on standard pituitary MRI even when including a dynamic contrast enhanced sequences [4]. Further, even in patients with Cushing’s disease who have a micro-PitNET detected on MRI, guidelines suggest to confirm localization of the tumour within the pituitary gland through bilateral inferior petrosal sinus sampling (IPSS) [5]. This technique is considered the gold standard to confirm origin of adrenocorticotrope hormone hypersecretion. However, this invasive procedure has a risk of non-negligible complications and even neurologic damage. Similarly, following transsphenoidal surgery, sites of residual or recurrent disease may not be evident or readily distinguished from posttreatment changes [6], complicating redo surgery or adjuvant radiotherapy. Therefore, despite advancements in MR imaging modalities, more accurate imaging methods providing further information on activity and localization would prove beneficial for patients. Also, from another perspective, evaluation of metabolic characteristics of pituitary neuroendocrine tumours has potential to advance diagnostics. For instance, hormonal functionality of a pituitary incidentaloma is not always easy to confirm and MRI-based imaging provides primarily structural information, but little functional information, e.g. prognostic information on growth potential of the tumour. As, such molecular imaging could be of complementary value. …