Common mutations, domains, and off-label approaches

The EGFRvIII mutation lacks the L1 and CR1 domains, which are critical for ligand binding, so it becomes a key driver in tumor progression and is linked to poor prognosis \cite{Shinojima2003}. Therefore, exploring potential shared targets between GBM and ESCC with this mutation profile could lead to the development of effective therapies. A few approaches have emerged in the last few years that specifically target the vIII variants in EGFR \cite{Jain2018} \cite{O_Rourke_2017}. For example, Rindopepimut showed promising results in a phase-II multicenter trial with improved progression-free survival and overall survival metrics \cite{Schuster2015} . These could carry potential use as an off-label treatment for ESCC with EGFRvIII amplification. Alternatively, developing novel therapies that target EGFRvIII or its downstream signaling pathways could be considered for ESCC patients with this mutation profile. Further research and clinical trials are needed to validate these approaches, but they hold promise to improve outcomes for patients with ESCC and EGFRvIII amplification.