Osimertinib-induced syndrome of inappropriate secretion of antidiuretic hormone in oncogene-addicted lung adenocarcinoma: A case report.

BACKGROUND

Asian patients with metastatic non-small cell lung cancer (NSCLC) have a higher prevalence of epidermal growth factor receptor (EGFR) mutations compared to Caucasians, 30-50% and 15%, respectively. Osimertinib is a tyrosine kinase inhibitor approved as first-line therapy in patients with metastatic NSCLC harboring exon 19 or exon 21 EGFR mutations.

CASE PRESENTATION: We report a 68-year-old treatment-naïve Asian male patient with metastatic NSCLC harboring an exon 19 deletion mutation of EGFR treated with osimertinib. The patient developed an osimertinib-induced syndrome of inappropriate secretion of antidiuretic hormone (SIADH) after approximately two months of therapy. Following fluid restriction and osimertinib discontinuation, the hyponatremia improved significantly within one week. The patient was started on second-line erlotinib without any signs of hyponatremia after treatment initiation.

CONCLUSION

There is a lack of published data from randomized prospective clinical trials of osimertinib-induced SIADH in metastatic NSCLC. Further studies to evaluate the potential underlying mechanisms are warranted.