Early disease control with a biochemical response to aumolertinib after postoperative recurrence of EGFR-Mutant stage IIIA lung adenocarcinoma after icotinib, with EGFR T790M detected at recurrence: a Case Report.

Background: Epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs) are a standard treatment for EGFR-mutant non-small cell lung cancer (NSCLC). However, acquired resistance commonly develops after treatment with first- or second-generation EGFR-TKIs. Aumolertinib, a third-generation EGFR-TKI, has demonstrated efficacy in tumors harboring the EGFR exon 20 T790M resistance mutation. Case Presentation: A 57-year-old man with stage IIIA lung adenocarcinoma and a history of hypertension and long-term smoking underwent thoracoscopic lobectomy with intrapulmonary lymph node dissection. Postoperative molecular testing identified an EGFR exon 19 deletion, and adjuvant oral icotinib (375 mg/d) was initiated. After treatment discontinuation, disease recurrence was detected on PET-CT involving the right hilar lymph nodes and a right pleural/subpleural lesion, which was confirmed by biopsy. Repeat molecular testing revealed concurrent EGFR exon 19 deletion and EGFR exon 20 T790M mutation. After 1 month of aumolertinib treatment, the target lesion decreased in size from 24 to 23 mm and was assessed as stable disease according to RECIST version 1.1, whereas the serum CEA level decreased from 24.19 to 4.35 ng/mL, indicating early disease control with a biochemical response. Conclusion: This case demonstrates early disease control and a biochemical response to aumolertinib treatment in recurrent NSCLC with an EGFR exon 20 T790M mutation detected at recurrence. It also highlights the importance of repeat molecular testing to guide therapeutic decisions.