All included patients had histologically confirmed EGFR-mutant lung cancer followed by biopsy-proven SCLC transformation. Fifty-nine patients were identified, making this one of the larger multicenter real-world datasets examining this specific resistance phenotype.

The median age was 57.8 years, and 76.3% of patients carried an EGFR exon 19 deletion.

Most patients had initially presented with metastatic disease, and 57 of 59 had received first-line EGFR-TKI therapy. Median progression-free survival on initial EGFR-targeted therapy was 14 months, while the median interval from metastatic diagnosis to histologic SCLC transformation was 22 months.