Non-small-cell Lung Cancer with Epidermal Growth Factor Receptor L861Q-L833F Compound Mutation Benefits from Both Afatinib and Osimertinib: A Case Report

Background: Epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs) have been adopted as the standard of care for non-small cell lung cancer (NSCLC) patients harboring sensitizing mutations. Besides the two common mutations exon 19 deletion and L858R, which together comprise approximately 85% of mutations in NSCLC, rare mutations also exist, including point mutations, deletions, and insertions spanning exons 18-25. However, the responsiveness of uncommon mutations to EGFR TKIs remains elusive and attracts increasing interest.

Case Summary: Herein, we report a 55-year-old male patient with stage IV NSCLC harboring a rare L833F-L861Q compound mutation . The patient achieved a partial response to first-line treatment with afatinib and a progression-free survival of 10 mo. After afatinib failure, the patient received multiple line treatments with chemotherapy. Upon disease progression, the heavily pretreated patient was treated with osimertinib and bevacizumab, and both lung lesion and brain metastases were stable for more than 3 mo. He had an overall survival of 25 mo.

Conclusion: Our case revealed that both afatinib and the osimertinib + bevacizumab combination demonstrated clinical efficacy in NSCLC harboring an L833F-L861Q compound mutation. The results provide more therapeutic options for patients with rare compound mutations.