Abstract YO37
Case summary
Background: Radioiodine refractory (RAIR) PTC is challenging to manage in the presence of brain metastasis. The use of antiangiogenic drugs such as lenvatinib and sorafenib pose a bleeding risk in such situations. BRAF mutation is commonly seen in RAIR PTC. The neoadjuvant use of BRAF inhibitors has been described in anaplastic thyroid cancer but have limited role in PTC. They have been shown to restore RAI avidity in RAIR PTC. I present a case of recurrent metastatic PTC where treatment with dabrafenib and trametinib (DT) were used both in neoadjuvant and adjuvant setting.
Case Presentation: 71-year-old man with PTC originally diagnosed in June 2020 underwent a total thyroidectomy in June 2020 and 126 mci of RAI in January 2021. He was then found to have biopsy proven recurrence in his lymph nodes in September 2023. Imaging at that time showed a 2.9 cm mass in the right thyroid bed that with a mass effect on IJV. He was also experiencing cognitive issues and blurry vision. MRI brain showed a solitary brain metastasis. He was then referred to us in October 2023. Cross sectional scans confirmed diffuse multiple bilateral pulmonary nodules and right neck lymph nodes concerning for metastases. He was treated with 20 Gy of SBRT to his left occipital intra axial nodule metastasis. Given that he had disease in his neck and chest as well, systemic therapy was considered. Due to the concern of brain bleed with lenvatinib, molecular testing on his tumor was sought. This showed BRAF positivity. DT was started at a dose of 150 mg BID and 2 mg daily respectively. PETCT in 3 months showed resolution of disease in his brain and his lungs. His neck disease was treated with surgery in February 2024.His thyroglobulin values remained detectable. DT was resumed. He received 150 mci of RAI while on these medications although diagnostic scan was negative. Post treatment scan showed uptake in a right supraclavicular lymph node and right lung. DT was stopped 3 days after RAI.
Conclusion: Checking for druggable molecular targets may provide a safer approach in treating patients with advanced thyroid cancer involving brain metastasis. Targeted therapies can be used safely in the neoadjuvant setting as well as help restore RAI avidity in the adjuvant setting in RAIR PTC.