111In-pentetreotide scintigraphy and 18F FDG PET-CT in differentiated thyroid carcinoma metastases with negative whole body radioiodine scan.

Metastases of differentiated thyroid cancer (DTC) can lose affinity to radioiodine with the passage of time, with resultant difficulty in management. Thyroid tumors are known to express somatostatin receptors and therefore 111In-pentetreotide, somatostatin analogue, can visualize tumors with high concentration of somatostatin receptors. We report a case of I-131 whole body scan (WBS) negative recurrent metastatic papillary thyroid carcinoma with positive 18F FDG PET-CT and 111In-pentetreotide scan. Somatostatin receptor scintigraphy (SRS) with 111In-pentetreotide may be useful both in the staging and monitoring of patients with non-iodine avid carcinoma of the thyroid. 111In-pentetreotide scan positive patients are potential candidates for somatostatin receptor-targeted therapy.