What happened, in summary

A 72-year-old woman with EGFR-mutated lung cancer received osimertinib for about 11 months. At progression, the cancer had changed into spindle cell carcinoma, a sarcomatoid form. The tumor had a TP53 p.L201fs alteration in the original diagnostic specimen. Blood testing at progression still detected the EGFR exon 19 deletion and did not identify another resistance mechanism. She then received carboplatin and pemetrexed chemotherapy. Her condition deteriorated quickly, and she died 3 months later. Unlike the other transformed cases in the same series, her tumor did not change into small cell lung cancer but instead developed a spindle-cell sarcomatoid pattern, again requiring a change away from first-line osimertinib.