What happened, in summary

A 67-year-old woman was diagnosed with Stage IV lung adenocarcinoma involving the brain, lungs, bones, and left adrenal gland. Testing found an EGFR exon 19 deletion, and she began osimertinib as first-line targeted therapy.

After 42 days, she developed shortness of breath and was diagnosed with osimertinib-related interstitial lung disease. Osimertinib was stopped and corticosteroids rapidly improved the lung inflammation. She declined cytotoxic chemotherapy and instead switched to afatinib, achieving a partial response without another episode of interstitial lung disease.

Eighteen months later, new lung metastases appeared. She continued afatinib, but worsening brain metastases eventually required whole-brain radiation. The cancer later spread to the meninges, and a blood test detected an acquired EGFR T790M resistance mutation. With limited alternatives, she and her family chose to retry osimertinib at a lower dose together with corticosteroids. The rechallenge reduced the tumor and did not trigger another episode of interstitial lung disease in the latest documented follow-up.