A Case of Renal Immune-related Adverse Event during Neoadjuvant Chemotherapy with Pembrolizumab for Breast Cancer

Abstract

A 63-year-old woman was incidentally diagnosed with a right breast mass on computed tomography. Further evaluation led to a diagnosis of triple-negative breast cancer (cT2N1M0, cStage II B), and neoadjuvant chemotherapy, including pembrolizumab, was initiated according to the KEYNOTE-522 trial. After completing one cycle of the second phase of treatment, the patient developed Grade 4 acute kidney injury. Renal biopsy revealed tubulointerstitial nephritis, and she was diagnosed with renal immune-related adverse events caused by immune checkpoint inhibitor therapy. Although her renal function improved with corticosteroid treatment, neoadjuvant chemotherapy was discontinued and surgery was performed. Postoperative adjuvant therapy was not administered, and corticosteroid treatment was continued. However, the patient subsequently developed a sacral fracture due to steroid-induced osteoporosis, requiring additional management. As renal immune-related adverse events become more severe, early diagnosis and appropriate interventions are essential. Furthermore, comprehensive management, including monitoring of steroid-related complications, is crucial. To our knowledge, no prior reports exists regarding renal immune-related adverse events in patients with breast cancer in Japan. We report this rare case with a review of the relevant literature.