Background: Non-small cell lung cancer (NSCLC) accounts for the majority of all lung cancer cases. Causes of NSCLC are typically identified through molecular testing for EGFR and other mutations. Around half of Asian patients with NSCLC, particularly non-smoking women, have EGFR mutations. Most patients with ipsilateral NSCLC typically have a single common EGFR mutation in exons 18-21. It is extremely rare for patients with bilateral primary NSCLC to harbor two different EGFR mutations. Case summary: We present a 70-year-old non-smoking Vietnamese patient diagnosed with early bilateral primary NSCLC with the presence of EGFR in both exon 18 and exon 19. The complexities of diagnosis and treatment for this case resulted in surgical intervention on the left lung and targeted therapy with afatinib for the right lung. Progression arrest was observered in a period of 12 months. Conclusion: This case highlights a rare instance of synchronous bilateral NSCLC in a non-smoking, 70-year-old Vietnamese woman with complex management, underscoring the challenges of treating synchronous primary tumors with different genetic profiles.

Background: A T263P mutation is one of the rare EGFR mutation, located in 7p11.2, a change in the amino acid residue at position 263 in the epidermal growth factor receptor protein where L-threonine has been replaced by L-proline. This missense mutation in the EGFR extracellular (EC) domain is poor-known about EGFR EC domain mutations in lung cancer. Purpose: In this study, we firstly reported a patient with advanced lung adenocarcinoma haboring a rare EGFR mutations of T263P alone who benefited from first-line treatment with afatinib in Vietnam. Results: This patient achieved a partial response and had a progression-free survival of 5 months. After disease progression, this patient was subsequently administered several chemotherapy regimens and had an overall survival of 17 months. Conclusion: NSCLCs with rare T263P mutation reveal the response to afatinib, however prognosis is often poor.