Switching to afatinib for osimertinib-associated renal injury in lung cancer and chronic kidney disease: Case report

Epidermal growth factor receptor tyrosine kinase inhibitor (EGFR–TKI), including osimertinib, have been reported to cause nephrotoxicity. However, distinguishing true renal impairment from pseudo-renal dysfunction due to transporter inhibition (pseudo-AKI) remains challenging, particularly in patients with chronic kidney disease (CKD). We report a case of a 76-year-old man with pre-existing CKD stage G3bA3 who developed a rapid increase in serum creatinine levels 8 days after initiating osimertinib for EGFR L858R mutation-positive non-small cell lung cancer (NSCLC). Anticancer therapy was subsequently modified by switching to dose-adjusted afatinib, allowing for continued EGFR–TKIs treatment without further renal deterioration. Renal function remained stable for more than 2 years under joint oncological and nephrological management. This case highlights the clinical utility of an integrated renal assessment using cystatin C and tubular injury markers in differentiating true renal injury from pseudo-AKI. This approach supports the clinical decision to switch to an alternative EGFR–TKI in patients with CKD, thereby enabling the safe continuation of targeted cancer therapy.