What happened, in summary

This 74-year-old non-smoking woman was diagnosed with left lower-lobe lung adenocarcinoma carrying an EGFR exon 19 deletion. She underwent left lower lobectomy with systematic lymph-node dissection. The postoperative pathologic stage was pT2aN2M0 / Stage IIIA, meaning mediastinal lymph-node disease was present but no distant metastasis was described. After surgery, she received 4 courses of adjuvant cisplatin and vinorelbine, followed by adjuvant osimertinib 80 mg daily. After 49 days on osimertinib, she developed respiratory distress and low oxygen levels, with oxygen saturation of 85% on room air during exertion. Blood tests showed elevated KL-6 and surfactant protein D, markers often used in interstitial lung disease evaluation, along with a markedly high D-dimer level. Chest CT showed diffuse ground-glass opacities in both lungs, and she was diagnosed with interstitial lung disease, a serious toxicity that required immediate interruption of the targeted therapy. Osimertinib was stopped immediately, and methylprednisolone 1 mg/kg/day was started. Despite steroid treatment, her breathing problems persisted and she developed leg edema. Four days after the interstitial lung disease diagnosis, D-dimer rose further, prompting contrast-enhanced CT. That scan showed thrombosis in the main trunk of the right pulmonary artery and in the right femoral vein, leading to diagnoses of pulmonary embolism and deep vein thrombosis. Apixaban 20 mg daily was started, and her symptoms and CT findings improved rapidly. Steroids were tapered and stopped after 6 weeks. During the next 9 months, she had no recurrence of interstitial lung disease, pulmonary embolism, or non-small cell lung cancer, despite stopping osimertinib early.