Late‐Onset Crizotinib‐Associated Renal Cysts With Subsequent Regression Following Dose Reduction: A Case Report

Crizotinib, an anaplastic lymphoma kinase (ALK)/ROS1/c-MET inhibitor, improves outcomes in ALK-positive non-small cell lung cancer (NSCLC) but can cause crizotinib-associated renal cysts (CARCs), a rare yet clinically relevant adverse effect. We report a case of a 68-year-old Korean male who developed complex renal cysts after 4 years of crizotinib therapy. Radiologic findings initially raised suspicion for either an abscess or a neoplastic lesion, leading to surgical resection. However, recurrent renal cysts developed during continued crizotinib therapy, and CARCs were subsequently suspected. A dose reduction was implemented, which led to cyst regression without compromising tumor control. This case highlights the need to recognize and manage late-onset toxicities during long-term treatment, emphasizing the clinical value of multidisciplinary evaluation and tailored dose adjustments.