What happened, in summary

A 74-year-old female non-smoker was diagnosed in January 2020 after routine imaging found a 3.5 cm mass in the right upper lung lobe. PET-CT showed high FDG uptake in the primary lung lesion and moderate uptake in ipsilateral mediastinal lymph nodes, with no distant metastasis. Brain MRI showed no intracranial metastasis. CT-guided biopsy confirmed lung adenocarcinoma, and tissue next-generation sequencing identified EGFR L858R and EGFR L861Q mutations. Her disease was staged as T2bN2M0, consistent with Stage III lung cancer. She received neoadjuvant osimertinib 80 mg daily for 12 weeks. Chest CT showed an approximately 80% partial response, allowing the team to proceed with surgery. In August 2020, she underwent right upper lobectomy and mediastinal lymph-node dissection. Pathology showed a pT1aN0 response with negative spread through air spaces. After surgery, she did not receive adjuvant therapy. At 42 months of follow-up, PET-CT and brain MRI showed no evidence of disease. This was a molecularly guided treatment path: EGFR testing led to neoadjuvant osimertinib, which produced major shrinkage before resection. Durable disease control was then maintained with surgery and surveillance alone after the 12-week osimertinib course. No metastatic sites, radiation, chemotherapy, or immunotherapy were described. The pathology shift from clinical T2bN2M0 to pT1aN0 after treatment shows why the preoperative osimertinib response was clinically meaningful. Negative spread through air spaces also supported a more favorable post-resection interpretation alongside the later PET-CT and brain MRI results. This distinction matters because the patient moved from clinically node-positive Stage III disease to pathologic pT1aN0 disease, making the surgical response a major part of the outcome.