177Lu-DOTATATE Therapy in Radioiodine-refractory Differentiated Thyroid Cancer: A Single Center Experience

Introduction Patients with radioiodine-refractory differentiated thyroid cancer (RrDTC) have a rather poor prognosis and are in need of novel treatments. As RrDTCs can in some cases express somatostatin receptors (SSRT), targeting of these receptors by Ga-68/Lu-177-DOTATATE could evolve as a novel theranostic option. Methods Five RrDTC patients with limited further therapeutic options and documented expression of SSRT using Ga-68-DOTATATE-PET/CT received 2 to 4 cycles of PRRT with Lu-177-DOTATATE. Response to therapy was assessed by thyroglobulin (Tg) and morphological and metabolic criteria based on interim and follow-up Ga-68-DOTATATE-PET/CTs. Analysis was performed on a per-patient basis. Results In the post-therapy evaluation, only one out of five patients showed a partial response, whereas three patients had a progressive disease. One patient had discordant findings between stable imaging results albeit rising Tg levels. Conclusion In this case study of five patients, Lu-177-DOTATATE therapy showed only heterogeneous response and efficacy in RrDTC patients despite good lesional uptake in pre-therapeutic PET.