Use of indium-111 pentetreotide somatostatin receptor scintigraphy to detect recurrent thyroid carcinoma in patients without detectable iodine uptake.

We conducted a prospective evaluation of somatostatin receptor scintigraphy (SRS) for the diagnosis of recurrent vesicular or papillary thyroid carcinoma in 16 patients with no detectable iodine uptake. SRS was performed 1, 4 and 24 h after intravenous injection of 137-200 MBq of indium-111 pentetreotide. Results were interpreted in terms of assumed presence of tumoral tissue: there were three true-positives (19%), one false-positive (6%) and 12 false-negatives (75%). The three true-positive patients had multiple lesions visible on computerized tomography. SRS was negative in all patients with a high thyroglobulin level alone. In addition, we analyzed the consequences of interpretative criteria and somatostatin receptor expression variability for SRS positivity as well as the risk of false-positives. We conclude that when iodine uptake cannot be demonstrated in patients with suspected recurrence of differentiated thyroid carcinoma, SRS would not appear to contribute to diagnosis, and that interpretative criteria commonly used for tumours with a high receptor density may be too restrictive for tumours with a low receptor density.