Combination of Dabrafenib and Trametinib in Patients with Metastatic BRAFV600E-Mutated Thyroid Cancer.

Purpose:BRAF mutations are detected in 30-80% of papillary thyroid cancer (PTC) cases. Dabrafenib and trametinib showed promising antitumor activity in patients with BRAFV600E-mutated metastatic melanoma and non-small cell lung cancer. This study aimed to evaluate the efficacy and safety of dabrafenib and trametinib in patients with metastatic BRAFV600E-mutated thyroid cancer. Materials and Methods:This was a retrospective study to evaluate the efficacy of dabrafenib and trametinib in patients with metastatic BRAFV600E-mutated PTC. The patients received dabrafenib 150 mg twice daily and trametinib 2 mg once daily at the Samsung Medical Center. This study evaluated the progression-free survival (PFS), objective response rate (ORR), disease control rate (DCR) overall survival (OS), and safety of dabrafenib and trametinib. Results:Between December 2019 and January 2022, 27 PTC patients including 8 patients with poorly differentiated or anaplastic transformation, received dabrafenib and trametinib. The median age was 73.0 years, and the median follow-up period was 19.8 months. The majority (81.5%) had undergone thyroidectomy, while 8 patients had received prior systemic treatments. ORR was 73.1%, with 19 partial responses, and DCR was 92.3%. Median PFS was 21.7 months, and median OS was 21.7 months. Treatment-related adverse events included generalized weakness (29.6%), fever (25.9%), and gastrointestinal problems (22.2%). Dose reduction due to adverse events was required in 81.5% of the patients. Conclusion:Dabrafenib and trametinib demonstrated a high ORR with promising PFS; however, most patients with BRAFV600E-mutated metastatic PTC required a dose reduction.