ALK-rearranged lung adenocarcinoma: sustained partial response on reduced-dose crizotinib after renal cysts

What happened, in summary

This 58-year-old Korean man had a 33 pack-year smoking history and had quit smoking 5 years earlier. In September 2015, an incidental lung mass was found in the left lower lobe, and staging showed no distant metastasis. In October 2015, he underwent video-assisted thoracoscopic wedge resection. Pathology showed ALK-rearranged lung adenocarcinoma, pT4N0M0, and FISH confirmed ALK gene translocation in more than 15% of tumor cells. Because the resection was incomplete, he received concurrent chemoradiotherapy with 6000 cGy. In April 2018, CT showed enlargement of left lower mediastinal and interlobar lymph nodes. EBUS-guided biopsy confirmed recurrent adenocarcinoma, so crizotinib 250 mg twice daily was started in May 2018. The cancer entered partial remission. In October 2019, additional radiotherapy of 5000 cGy was given for oligoprogression. During long-term crizotinib treatment, kidney findings became a major issue. A small right renal cyst appeared in 2021, and by 2022 imaging showed a larger right kidney lesion concerning enough to raise the possibility of malignancy. Urinalysis showed no hematuria and urine cytology was negative, but the lesion remained suspicious enough for surgery. Partial nephrectomy in November 2022 showed an old abscess with fibrous capsule formation, not kidney cancer. Crizotinib was continued, but by February 2024 cysts in both kidneys had enlarged. After multidisciplinary review, the cysts were considered possible crizotinib-associated renal cysts. Because his lung cancer remained controlled, the dose was reduced directly to 250 mg once daily in June 2024. As of June 2025, imaging showed significant cyst regression, renal MRI confirmed complete remission of the cysts, and there was no lung cancer progression.