Stage 4 EGFR-mutant lung cancer controlled on gefitinib after osimertinib intolerance

What happened, in summary

A 78-year-old Japanese woman who had never smoked was diagnosed with Stage IVB lung adenocarcinoma, cT1cN0M1c, with an EGFR exon 21 L858R mutation. She began first-line osimertinib 80 mg daily. After 51 days, she developed grade 3 osimertinib-induced interstitial lung disease. CT showed a hypersensitivity-pneumonia pattern, and she required oxygen up to 2 L by nasal cannula. Osimertinib was discontinued. She was treated with methylprednisolone 1000 for 3 days, followed by prednisolone 45 mg daily, and the steroid dose was tapered until treatment was completed. When prednisolone ended, her lung cancer had not progressed, but she strongly wanted to continue active anticancer treatment. Her team therefore started gefitinib 250 mg daily as second-line EGFR-targeted therapy. The formal diagnosis was Stage IVB lung adenocarcinoma with cT1cN0M1c classification; specific metastatic organs were not named for this patient. As of August 2024, she remained on gefitinib with no recurrence of interstitial lung disease. Her latest status is best described as ongoing care, because the case reports continued gefitinib and no recurrence of interstitial lung disease rather than remission or no evidence of cancer. Other cases in the same article involved pleural effusion, lung metastases, bone metastases, or liver metastases, but those sites were not stated for Case 6.