BACKGROUND: Relapsed/metastatic anaplastic thyroid carcinoma (R/M ATC) is associated with poor prognosis. Approximately 40% of ATCs harbor the BRAFV600E mutation, for which targeted therapy is available. However, the clinical characteristics of BRAFV600E-mutant versus wild-type ATC and the role of liquid biopsy (LB) for molecular assessment and monitoring remain incompletely defined. METHODS: Consecutive patients with R/M ATCs treated at a tertiary referral center were stratified as BRAF wild-type (Cohort A) or BRAFV600E-mutant (Cohort B). Patients received chemotherapy, dabrafenib and trametinib (BRAF/MEKi), immune checkpoint inhibitors (ICI) or best supportive care. Tumor tissue (TB) was analyzed by RT-PCR and/or next-generation sequencing (NGS). Circulating cell-free DNA was assessed by droplet digital PCR (ddPCR) and/or a 52-gene NGS panel on LB at baseline in both cohorts and longitudinally in Cohort B. Clinical characteristics, treatment outcomes, and concordance between TB and LB were evaluated. RESULTS: Between 2018 and 2021, 24 patients were included (13 Cohort A, 11 Cohort B). BRAFV600E tumors more frequently presented with metastatic disease at diagnosis (81.8% vs. 15.4%, p = 0.003). Overall, 79% received first-line therapy and 41.6% second-line treatment. All patients in Cohort B received BRAF/MEK inhibitors, achieving a median progression-free survival of 3.2 months (95% CI 1.2-17.5). Concordance for BRAFV600E status between TB and LB assessed by ddPCR was 93.7% (specificity 100%, sensitivity 85.7%). Among 12 paired TB/LB NGS analyses, overall mutation concordance was 30%. In longitudinal assessment, LB anticipated disease progression in 3 of 6 cases and, in one case, identified emerging secondary alterations during BRAF/MEK inhibitor therapy. CONCLUSIONS: BRAFV600E-mutant ATC displays distinct clinical features and improved survival when treated with targeted therapy; ddPCR-based liquid biopsy provides a rapid and sensitive method for BRAFV600E detection and may support timely therapeutic decision-making. Serial LB analysis may contribute to disease monitoring and detection of resistance mechanisms in selected patients.
Colombo et al. (Tue,) studied this question.