Peptide receptor radionuclide therapy for non-radioiodine-avid differentiated thyroid carcinoma

patients with progressive metastatic (or recurrent) differentiated thyroid carcinoma (DTC) who do not respond to radioiodine therapy or do not show uptake on radioiodine scintigraphy, treatment options are few. Because these tumors may express somatostatin receptors, peptide receptor radionuclide therapy might be effective. We evaluated the therapeutic efficacy of the radiolabeled somatostatin analog Lu-177-1,4,7,10-tetraazacyclododecane-N,N',N",N"'-tetraacetic acid(0) (DOTA), Tyr(3)-octreotate (Lu-177-DOTATATE) in patients with DTC. The uptake of radioactivity in tumors was also studied in relation to treatment outcome. Methods: Five patients with DTC (3 with Hurthle cell thyroid carcinoma [HCTC], 1 with papillary thyroid carcinoma [PTC], and 1 with follicular thyroid carcinoma [FTC)) were treated with 22.4-30.1 GBq of Lu-177-DOTATATE. Response to therapy was evaluated with CT. Uptake on Lu-177-DOTATATE scintigraphy (24 h after treatment), expressed as percentage of injected dose, was compared with uptake on pretherapy In-111-octreotide scintigraphy (24 h after injection). Results: After the last treatment with Lu-177-DOTATATE, 1 patient with HCTC had stable disease as a maximum response, 1 patient with HCTC had minor remission (tumor shrinkage between 25% and 50%), and 1 patient with HCTC had partial remission (shrinkage greater than or equal to50%). The responses in PTC and FTC were stable disease and progressive disease, respectively. A decrease in serum thyroglobulin level was found in patients with HCTC. Patients with minor and partial remissions had the highest Lu-177-DOTATATE-to-In-111-diethylenetriamine pentaacetic acid(0)-octreotide (In-111-octreotide) uptake ratios (3.2 and 2.4, respectively) whereas the other patients had uptake ratios smaller than 1.5. Conclusion: Lu-177-DOTATATE therapy can be effective in patients with progressive DTC who have no therapeutic options and sufficient uptake of In-111-octreotide in tumor lesions as shown on In-111-octreotide scintigraphy. This finding is especially important in patients with HCTC, because they cannot benefit from radioiodine therapy because of non-iodine-avid lesions at diagnosis.