The prognostic impact of age in different molecular subtypes of breast cancer: a population-based study

Background The aim of current study was to use competing risk model to calculate the potential differences that age played in the prognosis of different breast cancer subtypes. Methods The cohort was selected from Surveillance, Epidemiology, and End Results (SEER) program. The cumulative incidences of death (CID) was assessed for breast cancer caused deaths and other causes of mortality. The multivariate Cox proportional hazards regression model and the multivariate subdistribution hazard (SH) model were used to evaluate the prognostic value of age in different breast cancer subtypes. Results We involved 33,968 breast cancer patients into our cohort. We found older patients had worse overall survival (OS) than young patients in hormone receptor positive and human epidermal growth factor receptor 2 positive breast cancer (HR+/HER2+) (≥40 vs. <40, HR = 2.07, 95% CI [1.28–3.35], p  < 0.05). However, when we used competing risk model, we found young age was an independent risk factor only for triple negative breast cancer (TNBC) (≥40 vs. <40, HR = 0.71, 95% CI [0.56–0.89], p  < 0.05). No association was found in other groups. Conclusion Our research was currently the largest sample size study and the first competing risk model-based study on the prognostic association between age and different breast cancer subtypes. We found <40 years patients had worse breast cancer specific survival (BCSS) than older patients in the TNBC subtype.