In patients receiving anthracyclines, NADPH oxidase polymorphism rs4673 protected against focal myocardial necrosis (odds ratio [OR], 0.11; 95% confidence interval [CI], 0.20-0.63) whereas rs1883112 was strongly associated with cardiac fibrosis (OR, 5.11; 95% CI, 1.59-16.43), which was present in all homozygotes.