Durable response to afatinib in an advanced lung adenocarcinoma patient with an EGFR L858R/G729A compound mutation: a case report

Of the epidermal growth factor receptor (EGFR) mutations in patients with non-small cell lung cancer (NSCLC), 10–15% are uncommon mutations. Most of the EGFR “major” uncommon mutations have shown responses to EGFR-tyrosine kinase inhibitors (TKIs). However, there is a lack of clinical data for other less common types of EGFR mutations and the response to EGFR-TKIs, occurring either alone or in combination with EGFR sensitizing mutations. We reported a 70-year-old Chinese man with no smoking history who was diagnosed with stage IVA lung adenocarcinoma. An exceptionally uncommon EGFR G729A mutation in EGFR exon 19 was detected concomitantly with EGFR L858R in exon 21 in tumor specimens by next generation sequencing (NGS). This patient obtained limited benefit from icotinib and the increase in symptoms of cough and chest tightness, so we decided to switch the treatment to afatinib. Our patient exhibited partial response to afatinib with progression-free survival of 10 months. Subsequently, an EGFR T790M mutation was detected in the second lung biopsy. Then, osimertinib was administered and the symptoms improved significantly and the progress-free survival was nearly 16 months. Our data suggests that patients with NSCLC who are positive for uncommon EGFR G729A mutations may benefit from treatment with afatinib.