What happened, in summary

A 61-year-old woman who had never smoked was diagnosed with Stage IV EGFR-mutant lung adenocarcinoma involving the contralateral lung and pleura. She began erlotinib soon after diagnosis and initially responded on imaging. Five months later, she developed night sweats and a dry productive cough. CT imaging still showed less cancer, but new patchy ground-glass changes had appeared in the right lung and left upper lobe. Bronchoscopy and biopsy found organizing pneumonia, non-necrotizing granulomas and chronic interstitial pneumonitis. Infection testing was negative, supporting a diagnosis of erlotinib-induced pneumonitis rather than infection. Erlotinib was stopped and prednisone 40 mg daily was started, with an initial improvement in symptoms and CT findings. Steroids were later tapered because of side effects. About 1 year after the original diagnosis, a repeat scan showed worsening left lower-lobe changes and enlarging nodules in both lungs, consistent with cancer progression. She then started afatinib 40 mg daily. Her cough and shortness of breath on exertion improved almost immediately. After 4 weeks, CT imaging showed a cancer response without recurrence of the inflammatory infiltrates. Afatinib was continued, and at the last follow-up she had stable metastatic lung cancer almost 3 years after diagnosis, with the earlier treatment-related pneumonitis remaining controlled.