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Background: The dabrafenib plus trametinib combination (DT) has revolutionized the treatment of BRAFV600E-mutated anaplastic thyroid carcinoma (BRAFm-ATC). However, patients eventually develop resistance and progress. Single-agent anti-PD-1 inhibitor spartalizumab has shown a median overall survival (mOS) of 5.9 months. Combination of immunotherapy with BRAF/MEK inhibitors (BRAF/MEKi) seems to improve outcomes compared with BRAF/MEKi alone, although no direct comparison is available. BRAF-targeted therapy before surgery (neoadjuvant approach) has also shown improvement in survival. We studied the efficacy and safety of DT plus pembrolizumab (DTP) compared with current standard-of-care DT alone as an initial treatment, as well as in the neoadjuvant setting. Methods: Retrospective single-center study of patients with BRAFm-ATC treated with first-line BRAF-directed therapy between January 2014 and March 2023. Three groups were evaluated: DT, DTP (pembrolizumab added upfront or at progression), and neoadjuvant (DT before surgery, and pembrolizumab added before or after surgery). The primary endpoint was mOS between DT and DTP. Secondary endpoints included median progression-free survival (mPFS) and response rate with DT versus DTP as initial treatments, and the exploratory endpoint was mOS in the neoadjuvant group. Results: Seventy-one patients were included in the primary analysis: n = 23 in DT and n = 48 in DTP. Baseline demographics were similar between groups, including the presence of metastatic disease at start of treatment (p = 0.427) and prior treatments with surgery (p = 0.864) and radiation (p = 0.678). mOS was significantly longer with DTP (17.0 months [confidence interval CI, 11.9–22.1]) compared with DT alone (9.0 months [CI, 4.5–13.5]), p = 0.037. mPFS was also significantly improved with DTP as the initial treatment (11.0 months [CI, 7.0–15.0]) compared with DT alone (4.0 months [CI, 0.7–7.3]), p = 0.049. Twenty-three patients were in the exploratory neoadjuvant group, where mOS was the longest (63.0 months [CI, 15.5–110.5]). No grade 5 adverse events (AEs) occurred in all three cohorts, and 32.4% had immune-related AEs, most frequently hepatitis and colitis. Conclusions: Our results show that in BRAFm-ATC, addition of pembrolizumab to dabrafenib/trametinib may significantly prolong survival. Surgical resection of the primary tumor after initial BRAF-targeted therapy in selected patients may provide further survival benefit. However, conclusions are limited by the retrospective nature of the study. Additional prospective data are needed to confirm this observation. [ABSTRACT FROM AUTHOR]

Background: The BRAFV600E mutation is the most common driver mutation in papillary thyroid cancer (PTC) and anaplastic thyroid cancer (ATC). This mutation is considered actionable and, for BRAFV600E-mutated ATC, a BRAF inhibitor (dabrafenib) in combination with an MEK inhibitor (trametinib) is FDA approved. BRAF inhibitors have also shown efficacy in BRAFV600E-mutated PTC. However, as with all targeted therapies, resistance to these drugs eventually develops. It is essential that we understand the mechanisms of resistance to the BRAF inhibitors in thyroid cancer to develop future strategies to effectively treat these patients and improve survival. Patients: Herein, we describe four patients with thyroid cancer treated with selective BRAF inhibitors, who developed a RAS mutation in addition to the BRAFV600E mutation at progression. Results: Patients 1 and 3 acquired a KRASG12V mutation in the progressive tumor, patient 2 acquired a NRASQ61K mutation in a progressive lymph node, and patient 4 acquired NRASG13D mutation on liquid biopsy performed at the time of radiographic disease progression. Conclusion: Similar to the melanoma experience, the emergence of RAS mutations appears to act as a mechanism of resistance to BRAF inhibitors in thyroid cancers. [ABSTRACT FROM AUTHOR]

Background: When achieved, complete surgical resection improves outcomes in anaplastic thyroid carcinoma (ATC). However, most ATC patients present with advanced inoperable disease, often with impending airway obstruction, increased hemorrhage risk, and significant dysphagia. Novel treatment strategies are critically needed to improve disease control and decrease locoregional morbidity. The objective of this study was to determine the feasibility and effectiveness of a neoadjuvant regimen by using dabrafenib with trametinib followed by surgical resection in patients with initially unresectable BRAFV600E-mutated ATC. Methods: Case series of six consecutive patients with BRAFV600E-mutated ATC diagnosed between January 2017 and February 2018. Pathologic confirmation of ATC was obtained before treatment. BRAFV600E status was ascertained via immunohistochemistry or sequencing of circulating tumor DNA. All patients received dabrafenib and trametinib (DT) followed by surgical resection and adjuvant chemoradiation. Three patients also received pembrolizumab. Results: Complete surgical resection was achieved in all patients. Histopathologic analyses of resected specimens showed high pathologic response rates with significantly decreased ATC viability and residual papillary thyroid carcinoma components. Overall survival at six months and one year was 100% and 83%, respectively. Locoregional control rate was 100%. Two patients died of distant metastases without evidence of locoregional disease at 8 and 14 months from diagnosis. The remaining four patients had no evidence of disease at the last follow-up. Conclusions: We report the first series in the literature of BRAFV600E-mutated ATC patients with locoregionally advanced disease treated with DT followed by surgical resection. We demonstrated feasibility of complete resection, decreased need for tracheostomy, high pathologic response rates, and durable locoregional control with symptom amelioration. [ABSTRACT FROM AUTHOR]