To better illustrate the current challenges in diagnosing and managing a patient under adjuvant ICI treatment, we present the case of a 67-year-old female patient with stage IIIB unresectable, epidermal growth factor receptor (EGFR)-mutated, non-small-cell lung cancer who was initially treated with chemoradiotherapy, followed by immunotherapy with durvalumab. This evidence concerns the gene EGFR and non-small cell lung carcinoma.