68Ga-PSMA PET/CT in radioactive iodine-refractory differentiated thyroid cancer and first treatment results with 177Lu-PSMA-617

Lisa H de Vries; Lutske Lodewijk; Arthur J A T Braat; Gerard C Krijger; Gerlof D Valk; Marnix G E H Lam; Inne H M Borel Rinkes; Menno R Vriens; Bart de Keizer

doi:10.1186/s13550-020-0610-x

⁶⁸Ga-PSMA PET/CT in radioactive iodine-refractory differentiated thyroid cancer and first treatment results with ¹⁷⁷Lu-PSMA-617

EJNMMI Res. 2020 Mar 6;10(1):18. doi: 10.1186/s13550-020-0610-x.

Authors

Lisa H de Vries¹, Lutske Lodewijk¹, Arthur J A T Braat², Gerard C Krijger², Gerlof D Valk³, Marnix G E H Lam², Inne H M Borel Rinkes¹, Menno R Vriens¹, Bart de Keizer⁴

Affiliations

¹ Department of Surgery, University Medical Centre Utrecht, Heidelberglaan 100, 3584, CX, Utrecht, The Netherlands.
² Department of Radiology and Nuclear Medicine, University Medical Centre Utrecht, Heidelberglaan 100, 3584, CX, Utrecht, The Netherlands.
³ Department of Endocrine Oncology, University Medical Centre Utrecht, Heidelberglaan 100, 3584, CX, Utrecht, The Netherlands.
⁴ Department of Radiology and Nuclear Medicine, University Medical Centre Utrecht, Heidelberglaan 100, 3584, CX, Utrecht, The Netherlands. B.deKeizer@UMCUtrecht.nl.

Abstract

Background: Differentiated thyroid carcinoma (DTC) is the most common type of thyroid cancer. Treatment with surgery, radioactive iodine (RAI), and TSH suppression is effective in most patients. Five to 15% of patients become RAI refractory and need alternative therapy; however, treatment options are limited. ⁶⁸Ga-PSMA PET/CT, originally developed for prostate cancer, is also applicable to other malignancies, including thyroid carcinoma. The uptake of PSMA in thyroid carcinoma gives opportunities for imaging and therapy of RAI-refractory DTC. The aim of this study was to analyze imaging on ⁶⁸Ga-PSMA PET/CT and evaluate the response to ¹⁷⁷Lu-PSMA-617 therapy in patients with RAI-refractory DTC.

Materials and methods: Five patients with RAI-refractory DTC underwent ⁶⁸Ga-PSMA PET/CT to determine their eligibility for ¹⁷⁷Lu-PSMA-617 therapy. ⁶⁸Ga-PSMA PET/CTs were analyzed visually and quantitatively. Response to ¹⁷⁷Lu-PSMA-617 therapy was evaluated using imaging and thyroglobulin (Tg) values.

Results: Tracer uptake suspicious for distant metastases was depicted in all ⁶⁸Ga-PSMA PET/CTs. Based on tracer uptake, three patients were eligible for ¹⁷⁷Lu-PSMA-617 therapy, of whom two were treated. One patient showed disease progression on imaging 1 month later, while her Tg values gradually increased from 18 to 63 μg/L in the months after treatment. Another patient showed partial, temporary response of lung and liver metastases. Her Tg levels initially decreased from 17 to 9 μg/L. However, 7 months after treatment, there was disease progression on imaging and Tg levels had increased to 14 μg/L. Imaging with ⁶⁸Ga-PSMA PET/CT could be compared to ¹⁸FDG PET/CT in three patients. Two patients showed additional lesions on ⁶⁸Ga-PSMA PET/CT, and one patient showed concordant imaging.

Conclusion: ⁶⁸Ga-PSMA PET/CT appears to have added value in patients with RAI-refractory DTC, as it is able to detect various types of lesions, some of which were not picked up by ¹⁸FDG PET/CT. Furthermore, ⁶⁸Ga-PSMA PET/CT might be used to identify patients eligible for treatment with ¹⁷⁷Lu-PSMA-617. One of the two patients who underwent ¹⁷⁷Lu-PSMA-617 therapy showed a modest, temporary response. To draw conclusions about the effectiveness of this therapy, more research is needed.

Keywords: Gallium; Lutetium; PET/CT; Prostate-specific membrane antigen; Radioactive iodine-refractory differentiated thyroid carcinoma; Theranostic.