Can peptide receptor radionuclide therapy (PRRT) be useful in radioiodine-refractory differentiated thyroid cancer?

We report on a 70-year-old man affected by radioiodine-refractory differentiated thyroid cancer (DTC) in whom metastases were treated by peptide receptor radionuclide therapy (PRRT). Seven years before, patient had undergone total thyroidectomy. Pathological examination was conclusive for DTC. The patient underwent some radioiodine treatments (RaIT). The last post-therapy whole body scan (pT-WBS) performed five days after RaIT did not show abnormal radioiodine uptake but serum thyroglobulin (Tg) value was high in absence of thyroglobulin-antibodies (Tg-Ab). In-111 DTPA-pentetreotide scintigraphy showed several lung lesions with high somatostatin receptor density. Patient underwent PRRT using Lu-177 DOTATOC. pT-WBS scan confirmed the metastases already demonstrated by In-111 DTPA pentetreotide but radioiodine negative.