Successful treatment of a lung adenocarcinoma patient with a novel EGFR exon 20-ins mutation with afatinib: A case report

RATIONALE: Comprehensive genomic profiling for non-small cell lung cancer (NSCLC) is likely to identify more patients with rare genetic alterations, including uncommon epidermal growth factor receptor (EGFR) gene mutation. PATIENT CONCERNS: A 63-year-old Chinese woman who had never smoked visited our lung cancer clinic due to a chronic cough. DIAGNOSIS: The patient was diagnosed with lung adenocarcinoma by transbronchial lung biopsy. An EGFR mutation (exon 20 insertion H773_V774insH, D770_N771insG, V769_D770insASV, D770_N771insSVD) was detected in the biopsy specimen by quantitative real-time PCR. INTERVENTIONS: The patient was treated with osimertinib first, and the progression-free survival (PFS) was 4.4 months. After the disease progressed, the second genetic test of pleural effusion suggesting the EGFR exon 20-ins mutation site changed to A767delinsASVD only. Then the patient was treated with afatinib with informed consent. OUTCOMES: The treatment of afatinib in this patient was successful, PFS was 7.4 months. LESSONS: To our knowledge, EGFR exon 20-ins mutation A767delinsASVD has never been reported, and the successful treatment of afatinib may provide a new therapeutic option for this type of exon 20 insertion mutations.