Abstract
BACKGROUND: The advent of immune checkpoint inhibitors (ICIs) has revolutionized the management of several types of solid cancers, including lung cancer, by boosting the body's natural tumor killing response. However, it is undeniable that only a small proportion of non-small cell lung cancer (NSCLC) patients with epidermal growth factor receptor (EGFR) mutations can achieve long-term responses and benefit from immunotherapy. CASE SUMMARY: Herein, we report the case of a 48-year-old man diagnosed with stage IV lung adenocarcinoma with an EGFR L858R mutation who was administered pembrolizumab monotherapy followed by pemetrexed and achieved a 10-month progression-free survival interval. In this case report, we show that ICIs were effective for our patient with EGFR-mutated NSCLC and discuss the characteristics of patients who can benefit from immunotherapy. CONCLUSION: We suggest that patients with EGFR-mutated NSCLC with high PD-L1 expression (defined as ≥ 25%), the L858R mutation, smoking history, or pemetrexed pretreatment may benefit from immunotherapy.