Somatostatin receptor scintigraphy of a patient with a giant invasive prolactinoma

A 41-year-old with a giant prolactinoma underwent In-111 pentetreotide (Oct reotide) imaging showing very intense tracer uptake in the region of the an terior skull base. In contrast, there was no significant response to Octreo tide therapy. Prediction of clinical responsiveness to Octreotide therapy i n patients with pituitary adenomas may depend on the presence of somatostat in receptor subtype 5. Pentetreotide does not avidly bind to this receptor subtype and therefore, cannot be used clinically to predict therapeutic Oct reotide responsiveness in patients with large prolactinomas.