The impact of age on outcomes of breast cancer in different hormone receptor and HER2 groups

OBJECTIVE: The aim of the current study was to explore the association between age and outcomes in breast cancer. METHODS: Patients during 2010–2015 were identified from the Surveillance, Epidemiology, and End Results (SEER) database. Overall survival (OS) and breast cancer-specific death (BCSD) were taken as endpoints. The restrict cubic spline graph (RCS) was used to explore the relationship between age and outcomes in patients, and the cumulative incidence of BCSD and non-BCSD was calculated using the Gray method. Age-specific gene expression profiles were studied using RNA sequence data from the Cancer Genome Atlas (TCGA) database to explore whether there were young age-related gene or gene sets. RESULTS: A total of 142,755 patients with breast cancer were included. The hazard ratio (HR) of OS for Patients with stage I-III breast cancer was roughly stable before 53 years old and increased significantly after that, and the HR of BCSD for these patients showed a U-shaped distribution when plotted against age, with patients younger than 50 years and patients older than 70 years experiencing the worst survival. Further stratified analysis according to molecular subtype revealed that the U-shaped distribution of the HR of BCSD with was only found in the Hormone receptor-positive/HER2-negative (HoR+/HER2-) subgroup. The cumulative incidence plots showed that young age was associated with worse BCSD in the breast cancer patients with stage I-III and HoR+/HER2- subgroup. In stage IV breast cancer, there was a linearity of the relationship between poor OS and increasing age. We failed to find any differentially expressed age-specific genes between 20–40 years and 41–60 years groups in 258 patients with stage I-III and HoR+/HER2- subtype. CONCLUSION: Young age could predict worse BCSD of patient with stage I-III and HoR+/HER2- breast cancer. The escalating therapy was recommended to young age breast cancer with stage I-III and HoR+/HER2- subtype.