The effectiveness of sequential afatinib and furmonertinib in an advanced lung adenocarcinoma with rare compound EGFR mutation (L833V/H835L).

Uncommon atypical mutations account for 10-15% of all epidermal growth factor receptor (EGFR) activating mutations in nonsmall-cell lung cancer (NSCLC). Tumors harboring rare EGFR mutations show highly heterogeneous responses to EGFR tyrosine kinase inhibitors (TKIs). There is insufficient clinical evidence for uncommon types of EGFR mutations, especially those with compound EGFR mutations. In addition, for those with uncommon compound EGFR mutations, few studies have focused on acquired resistance mechanisms and subsequent treatment strategies after disease progression on EGFR-TKIs. Here, a 66-year-old smoking male was diagnosed with lung adenocarcinoma accompanied by pleural metastasis. A rare L833V/H835L compound mutation in exon 21 of EGFR was detected in tumor biopsy by next-generation sequencing. Afatinib was used as first-line therapy and showed favorable efficacy. The patient continued afatinib treatment for a duration of 24 months. A new T790M mutation was detected with a rebiopsy after progression on afatinib. Then the patient received cryoablation therapy and a third-generation EGFR-TKI, furmonertinib. Our case suggests that a comprehensive screening for EGFR mutations should be conducted before and during treatment in clinical practice, and afatinib and furmonertinib could be first- and second-line treatment options in NSCLC patients harboring EGFR L833V/H835L mutations.