99mTc-MIBI radio-guided surgery for recurrent thyroid carcinoma: technical feasibility and procedure, and preliminary clinical results

The preliminary results of technetium-99m methoxyisobutylisonitrile (MIBI) radio-guided surgery (RGS) in patients with differentiated thyroid carcinoma (DTC) and iodine-131-negative (non-functioning) recurrent disease are reported. Eight consecutive DTC patients were selected for RGS on the basis of pre-operative imaging findings: a 99mTc-MIBI scan consistent with local recurrence was taken as the principal inclusion criterion. The RGS procedure that we developed consisted in the injection of a low dose of 99mTc-MIBI (37 MBq) in the operating theatre a few minutes before the beginning of the intervention, with use of a hand-held gamma probe for the intra-operative detection of 99mTc-MIBI-avid tumoural foci. Radioactivity was measured in tumoural foci both in vivo and ex vivo, in the background and in the tumoural bed after lesion extirpation. After follow-up for 2-10 months, stable normalisation of serum thyroglobulin (Tg) levels was observed in six out of the seven patients in whom, during the intervention, the gamma probe-detected radioactivity in the neck fell to background values after tumour extirpation. In another patient the persistence of high radioactivity levels in the tumoural bed after lesion removal correctly suggested disease persistence (deep tracheal infiltration). These preliminary data suggest the feasibility of RGS in DTC patients with locoregional non-functioning but 99mTc-MIBI-avid recurrence by injection of a low, 37 MBq dose of 99mTc-MIBI just before the beginning of the intervention. (orig.)