ERBB2 and breast cancer: The adjusted hazard ratio (HR) of 5-year mortality by age for women diagnosed at age 20 to 44 years with HER2 negative BC (HR = 2.63; 95% CI: 1.46 to 4.74) was markedly higher than for women diagnosed at age 45 to 55 years (HR = 1.67; 95% CI: 1.18 to 2.36), 56 to 69 years (HR = 1.67; 95% CI: 1.26 to 2.21), and 70 to 90 years (HR = 1.06; 95% CI: 0.86 to 1.30).