EGFR-RAD51 gene fusion NSCLC responsiveness to different generation EGFR-TKIs: two cases and review of the literature

Epidermal growth factor receptor (EGFR) gene fusions represent an extremely rare aberration, occurring in approximately 0.05-0.13% non-small cell lung cancer (NSCLC) patients. RAD51 is the most frequently involved partner gene in EGFR fusions, but other fusion partner genes have been described. To date, a considerable number of next-generation sequencing (NGS) panels still cannot detect these alterations due to the position of the breakpoint site, mainly involving intron 24 of EGFR. Current evidences show that such gene alteration is more likely to occur in lung adenocarcinomas of young, female, non-smoker patients. Also, brain metastases are frequently reported in these patients. Only very few cases in literature described clinical characteristics and outcomes of patients harboring EGFR gene fusions, reporting responses to 1st generation EGFR tyrosine kinase inhibitors (TKIs). Herein, we report the case of two young nonsmoker females with metastatic NSCLC harboring EGFR-RAD51 gene fusion, detected by FoundationOne DX1 assay, who responded to EGFR TKIs. The first patient initially received erlotinib, then switched to osimertinib for renal toxicity, while the second was treated with gefitinib. This is, to our knowledge, the first report describing response to the 3rd EGFR TKI osimertinib. Our experience highlights the need of a broader molecular profiling in young or never smoker NSCLC patients without detectable molecular aberration using standard NGS panels. Finally, further studies to assess the real prevalence of EGFR gene fusions and their spectrum of sensitivity to different EGFR TKIs are needed.