B2M and acute kidney injury: In multivariate Cox regression analysis, preexisting–CKD (HR 7.01, CI 95%: 2.04‐24.09; P = 0.002), serum β2M (HR 3.05, CI 95%: 1.10‐8.44; P = 0.03) and mucositis grade 3/4 (HR 1.29, CI 95%: 1.08‐1.53; P = 0.003) were retained as independent risk factors for AKI (Figure 1).