1655P Dabrafenib and trametinib in patients with metastatic BRAFV600E-mutated thyroid cancer

Papillary thyroid cancer (PTC) is usually treated successfully with surgery and radioactive iodine therapy (RAI), but in some RAI-refractory patients metastatic symptomatic disease, systemic could be considered. BRAF mutations are detected over 80% of PTC Korea. Dabrafenib plus trametinib showed promising efficacy melanoma or non-small cell lung BRAFV600E mutation. This study evaluated the safety dabrafenib BRAFV600E-mutated cancer. a retrospective poorly differentiated anaplastic transformation. Patients had disease progressed 12 months prior to treatment. received 150mg twice daily 2mg once as part Expanded Access Program at Samsung Medical Center. objective response rate (ORR), safety, tolerability trametinib. Between December 2019 January 2022, 25 (poorly feature, n=8). Median age was 73.0 years (range, 24-84), median follow-up 6.8 1.0-28.4). Twenty-two thyroidectomy (3 initial stage IV) 8 treatment (4 lenvatinib, 3 sorafenib, 1 pembrolizumab lenvatinib). The cycle 5.9 1.1-30.4). site distant metastasis (n=23), brain (n=3), bone (n=3). ORR 72.0% (18 PR) control 88.0%. progression-free survival (PFS) 6 83.6%. Treatment-related adverse events were pyrexia (48.0%), generalized weakness (24.0%), skin rash (12.0%). Dose reduction due event required 84.0% patients. high symptom improvement, however, majority needed dose PTC. Additional period for mature data PFS overall survival.