Purpose: Radioiodine nonavid thyroid cancer (TC) is a rare disease entity with a poor prognosis. Despite a multimodal therapeutic approach including surgery, chemotherapy, and external beam radiation, radioiodine nonavid TC accounts for a high number of TC-associated deaths. The aim of this investigation was to evaluate the response rate of progressive TC patients to treatment with the proteasome inhibitor bortezomib.
Materials and methods: Seven patients with inoperable, metastasized progressive TC proven to be radioiodine nonavid were included into this pilot study. Patients received bortezomib intravenously with a standardized dose of 1.3 mg/m on days 1, 4, 8, and 11. All patients underwent 3 therapeutic cycles with an interval of 10 days. [F]2-deoxy-2-fluoro-D-glucose positron emission tomography (F-FDG PET) and measurements of thyroglobulin levels were performed before, during, and after therapy, with a 6-week interval to post-therapeutic follow-up.
Results: Stable disease was seen after proteasome inhibitor therapy in 4 of the 7 patients. Two of the 7 patients showed decrease of maximum standardized uptake value in both post-therapeutic follow-up investigations, and one of these cases also had decreasing thyroglobulin levels. Two patients experienced stable disease during the posttherapeutic follow-up. Two patients showing a mixed response had an improvement in their clinical situation. One patient had rapidly progressive disease, and died 3 months after the last therapeutic cycle. Adverse events included mild polyneuropathy in 2 patients and alterations of the blood count up to WHO (World Health Organization) grade 2 in 5 patients.
Conclusion: Proteasome inhibitor treatment with bortezomib is a promising therapeutic approach in TC patients without an established treatment alternative. The development of a specific therapeutic regimen for the treatment of radioiodine nonavid TC is warranted.