What happened, in summary

An 84-year-old man presented with shortness of breath and a right-sided pleural effusion. Imaging showed a right lower-lobe lung tumor with pleural nodules, enlarged lymph nodes, and direct extension into the diaphragm and liver. Biopsy confirmed squamous cell carcinoma. Molecular testing found an EGFR L858R mutation, and PD-L1 testing showed a tumor proportion score of 5%. The cancer was classified as Stage IV.

He first underwent drainage of the pleural fluid and talc pleurodesis. Because of his overall health and treatment preferences, he started first-line osimertinib rather than cytotoxic chemotherapy. After four weeks, imaging showed substantial shrinkage of the lung mass, pleural nodules, and lymph nodes, consistent with a partial response, and his performance status improved.

The response was short-lived. Twelve weeks after starting osimertinib, new vertebral bone metastases appeared, establishing disease progression despite continued shrinkage in the lung and liver-invading mass. He and his family declined subsequent cytotoxic chemotherapy. Osimertinib was continued beyond progression in an effort to limit the remaining tumor burden.