Achievement of pathological complete response with osimertinib for EGFR-mutated lung adenocarcinoma

Background Tyrosine-kinase inhibitors (TKIs) of epidermal growth factor receptor (EGFR) usually provide a potent anti-tumor efficacy with robust radiographic response for non-small cell lung cancer (NSCLC) harboring activating mutations in the EGFR gene. However, first-generation EGFR-TKIs may provide only modest pathological response in the majority of EGFR-mutated NSCLC. Here, we present a case of EGFR-mutated adenocarcinoma in which a pathological complete response was revealed in histological specimens obtained during conversion surgery following systemic treatment using a third-generation EGFR-TKI. Case presentation A 61-year-old Japanese man was admitted to our hospital for salvage surgery. Four months prior to the admission, he had been diagnosed with unresectable adenocarcinoma (clinical stage IIIA/T4N1MO) originating from the right lower lobe. Chest computed tomography had revealed a 3.4-cm tumor and enlarged hilar nodes that invaded into the left atrium through the lower pulmonary vein. An activating EGFR-mutation (L858R) had been detected in the tumor specimen. Osimertinib monotherapy had provided a dramatic radiographic response. The patient was diagnosed with potentially resectable disease after 4 months' osimertinib treatment and was referred to our hospital. Complete resection with right lower lobectomy and combined resection of the left atrium was achieved. Pathological examination showed no viable tumor cells in the resected specimens. Postoperative course was uneventful. The patient is alive without tumor recurrence at 2 years after surgery. Conclusions Pathological complete response was achieved with systemic treatment with osimertinib prior to surgery. Conversion surgery after osimertinib treatment may be safe and effective for NSCLC harboring activating EGFR-mutations.