Gain of Aggressive Histological and Molecular Patterns after Acquired Resistance to Novel Anti-EGFR Therapies in Non-Small Cell Lung Cancer.

Novel anti-EGFR therapies target resistance to standard-of-care anti-EGFR in patients with metastatic lung cancer. We describe tumors at progression versus at the initiation of novel anti-EGFR agents in patients with metastatic lung adenocarcinoma harboring EGFR mutation. This clinical case series reports the histological and genomic features and their evolution following disease progression under amivantamab or patritumab-deruxtecan in clinical trials. All patients had a biopsy at disease progression. Four patients harboring EGFR gene mutations were included. Three of them received anterior anti-EGFR treatment. Median delay to disease progression was 15 months (range: 4-24). At progression, all tumors presented a mutation in the TP53 signaling pathway associated with a loss of heterozygosis (LOH) of the allele in 75% (n = 3), and two tumors (50%) presented an RB1 mutation associated with LOH. Ki67 expression increased above 50% (range 50-90%) in all samples compared to baseline (range 10-30%), and one tumor expressed a positive neuroendocrine marker at progression. Our work reports the potential molecular mechanisms of resistance under novel anti-EGFR in patients with metastatic EGFR-mutated lung adenocarcinoma, with the transformation to a more aggressive histology with acquired TP53 mutation and/or the increase in Ki67 expression. These characteristics are usually found in aggressive Small Cell Lung Cancer.