111In-Octreotide Scintigraphy for Identification of Metastatic Medullary Thyroid Carcinoma in Children and Adolescents

Abstract

Most medullary thyroid cancers (MTC) express somatostatin receptors; therefore, (111)In-octreotide somatostatin receptor scintigraphy (SRS) may be useful in detecting sites of metastases in children with MTC. The aim of the study was to evaluate tumor metastases in children and adolescents with MTC using SRS in comparison to conventional imaging. A case series was conducted as part of baseline evaluation for cancer treatment protocol at the National Institutes of Health Clinical Center. Eleven patients with a median age of 15 (range, 9-17) yr participated in the study, 10 with histologically proven, metastatic MTC due to the M918T mutation of the RET protooncogene, and one with a known RET polymorphism. After receiving 0.086 mCi/kg (111)Indium-pentreotide, patients were examined with a single photon emission computed tomography scan 4 and 24 h after injection. Baseline conventional imaging, including computed tomography (neck, chest, abdomen, ± pelvis, adrenals), magnetic resonance imaging (neck), and bone scan, was performed on all patients. SRS results were compared with conventional imaging. Five of the 11 patients had abnormal findings on SRS. Of the 53 total target lesions present in the patients, only 24.5% were accurately identified through SRS. SRS appears to be less sensitive than conventional imaging at detecting the full extent of metastatic disease in children and adolescents with hereditary MTC. SRS incompletely identified sites of tumor and failed to visualize small sites of tumor or liver and lung metastases, and it has a limited role in the evaluation of metastatic disease in pediatric MTC patients.