INTRODUCTION: EGFR exon 20 insertions comprise 4% to 9% of EGFR mutated NSCLC. Despite being an oncogenic driver, they are associated with primary resistance to EGFR tyrosine kinase inhibitors (TKIs). We hypothesized that dual EGFR blockade with afatinib, an irreversible EGFR TKI, and cetuximab, a monoclonal antibody against EGFR, could induce tumor responses.
METHODS: Four patients with EGFR exon 20 insertion-positive NSCLC were treated with afatinib 40 mg once daily and cetuximab 250 mg/m2 to 500 mg/m2 every 2 weeks.
RESULTS: All patients had stage IV adenocarcinoma of the lung harboring an EGFR exon 20 insertion mutation. Previous lines of treatment consisted of platinum doublet chemotherapy (n = 4) and EGFR TKI (n = 2). Three of four patients showed a partial response according to Response Evaluation Criteria in Solid Tumors (RECIST 1.1). Median progression-free survival was 5.4 months (95% confidence interval: 0.0 - 14.2 months; range 2.7 months - 17.6 months). Toxicity was manageable with appropriate skin management and dose reduction being required in two patients.
CONCLUSIONS: Dual EGFR blockade with afatinib and cetuximab may induce tumor responses in patients with EGFR exon 20 insertion-positive NSCLC.