Octreotide scintigraphy in patients with differentiated thyroid carcinoma: Contribution for patients with negative radioiodine scan

Somatostatin receptor scintigraphy (SRS) was evaluated in 25 differentiated thyroid carcinoma (DTC) patients. All DTC patients had elevated thyroglobulin levels. A total body scan (TBS) was performed 4 and 24 h after injection of indium-111-DTPA-Phe-octreotide. Group 1 included 16 patients with negative ¹³¹I TBS; group 2 had 9 patients with positive ¹³¹I TBS. SRS results were compared to the results of conventional imaging methods in group 1 and to ¹³¹I TBS in group 2. ¹³¹I TBS was performed after administration of a therapeutic dose of ¹³¹I in all patients except one. SRS was positive in 20 of 25 (80%) patients. In group 1, SRS was positive in 12 of 16 patients; in the 3 patients with no previously known tumor site, SRS visualized one abnormal neck focus of uptake in two. In the other 13 patients, SRS disclosed unknown mediastinal foci in 2, but visualized less organ involvements and a smaller number of tumor sites than conventional imaging methods. In group 2, SRS was positive in 8 of 9 patients and visualized an identical (7 patients) or a smaller number (1 patient) of involved organs than ¹³¹I TBS; in 2 patients, SRS allowed the discovery of i abdominal and 1 bone tumor site. We suggest than SRS should guide imaging modalities in DTC patients with negative ¹³¹I TBS and be an alternative to ¹³¹I TBS in DTC patients unable to withdraw T₄ treatment.