Stage IIIA EGFR-mutated lung adenocarcinoma: surgery after osimertinib

What happened, in summary

This 64-year-old never-smoker was admitted in December 2022 after 2 weeks of dry cough. He had hypertension controlled with nifedipine and metoprolol, and a family history of lung cancer in his grandfather and brother. CT showed a 32 × 24 mm thick-walled cavitary mass in the dorsal segment of the left lower lobe, with irregular margins and a “Halloween pumpkin” appearance. PET showed strong FDG uptake in the lung mass and in hilar and mediastinal lymph nodes, while brain MRI showed no central nervous system involvement. Lung biopsy confirmed poorly differentiated adenocarcinoma with strong TTF-1 and CK7 staining and Ki-67 of 60%. PD-L1 TPS was 15%. Next-generation sequencing detected an EGFR E746_A750 deletion, with tumor mutation burden of 5.01 mutations/Mb. The pretreatment stage was clinical Stage IIIA, T2aN2M0. After multidisciplinary discussion, he received neoadjuvant osimertinib 80 mg daily for 2 months. His cough improved, and the main side effect was grade 2 diarrhea controlled with loperamide. Imaging showed partial response: the mass shrank to 20 × 17 mm and mediastinal lymphadenopathy resolved. He then underwent video-assisted thoracoscopic left lower lobectomy and thoracic lymphadenectomy. Final pathology showed residual poorly differentiated adenocarcinoma spanning 1.5 cm, no lymphovascular or visceral pleural invasion, and 0 of 15 lymph nodes involved. The postoperative stage was pT1cN0M0, Stage IA3. Because the tumor was poorly differentiated, he continued adjuvant osimertinib 80 mg daily. No preoperative chemotherapy or radiation was used perioperatively. As of July 2024, CT surveillance at 2, 6, and 12 months showed no recurrence.