To the Editor,

I read Yamauchi et al. article [1] with great interest as they investigated the effectiveness and safety of adjuvant olaparib in a subset of Japanese patients with high-risk early breast cancer who had BRCA1- or BRCA2-mutations. This subset was drawn from the phase 3 OlympiA trial. They came to the conclusion that the efficacy and safety analysis results were consistent with the OlympiA population worldwide, indicating that the conclusions from the global study can be applied to clinical practice in Japan. As a secondary endpoint, safety outcomes were also examined, with adverse events such as pneumonitis, radiation pneumonitis, myelodysplastic syndrome, acute myeloid leukemia, and new primary cancer other than MDS or AML being of particular interest. Data on kidney function among olaparib-treated patients are lacking, though. In a recent study, the incidence of any acute kidney injury (AKI), which is defined as a rise in serum creatinine of 1.5 times or more from baseline in the first 12 months after treatment with olaparib or niraparib in patients with ovarian cancer, was examined. They found that of 269 patients, 60 (22.3%) developed AKI, including 43/194 (22.1%) olaparib-treated patients and 17/75 (22.7%) niraparib-treated patients. Only 9 of 269 (3.3%) had AKI attributable to the olaparib or niraparib According to their findings, AKI is frequently experienced after taking olaparib or niraparib, as well as a brief decline in eGFR; however, sustained AKI that can be directly attributed to olaparib or niraparib, as well as long-term estimated glomerular filtration rate decline, are rare [2]. In conclusion, AKI may be regarded as a side effect in high-risk, early breast cancer patients with BRCA1 or BRCA2 mutations who are taking olaparib.