USE OF IN-111 PENTETREOTIDE SOMATOSTATIN RECEPTOR SCINTIGRAPHY TO DETECT RECURRENT THYROID-CARCINOMA IN PATIENTS WITHOUT DETECTABLE IODINE UPTAKE

We conducted a prospective evaluation of somatostatin receptor scintig raphy (SRS) for the diagnosis of recurrent vesicular or papillary thyr oid 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 assume d presence of tumoral tissue: there were three true-positives (19%), o ne false-positive (6%) and 12 false-negatives (75%). The three true-po sitive patients had multiple lesions visible on computerized tomograph y. SRS was negative in all patients with a high thyroglobulin level al one. In addition, we analyzed the consequences of interpretative crite ria and somatostatin receptor expression variability for SRS positivit y as well as the risk of false-positives. We conclude that when iodine uptake cannot be demonstrated in patients with suspected recurrence o f differentiated thyroid carcinoma, SRS would not appear to contribute to diagnosis, and that interpretative criteria commonly used for tumo urs with a high receptor density may be too restrictive for rumours wi th a low receptor density.