What happened, in summary

A 51-year-old Japanese man with advanced lung adenocarcinoma received four courses of pembrolizumab, cisplatin, and pemetrexed. After the initial combination treatment, he continued with pembrolizumab and pemetrexed as maintenance therapy.

His kidney function declined gradually rather than through a sudden hospital presentation. After five courses of the modified treatment, creatinine had increased from 0.89 to 1.59 mg/dL. He was referred to a nephrologist for further evaluation.

A kidney biopsy was recommended and showed acute tubulointerstitial nephritis. Prednisone was started at 30 mg daily. Over the next three months, creatinine remained stable at approximately 1.5–1.6 mg/dL.

His renal decline developed across several maintenance cycles and was detected through laboratory monitoring. The biopsy confirmed inflammatory injury and supported corticosteroid treatment. Ongoing coordination between oncology and nephrology was important because the complication appeared while he was receiving both chemotherapy and immunotherapy as maintenance care.