Young Patients with Hormone Receptor-Positive Breast Cancer Have a Higher Long-Term Risk of Breast Cancer Specific Death

Purpose: Although it is widely accepted that hormone receptor (HR) status is associated with later post-diagnostic periods, a debate exists as to whether the association is independent of age. The aim of our study was to confirm the impact of HR status on later period breast cancer-specific death (LP-BCSD) and later period non-breast cancer-specific death (LP-non-BCSD) in different age subgroups. Methods: Surveillance, Epidemiology, and End Results databases were utilized to identify 181,108 breast cancer patients with > 5 years survival. The cumulative incidence of LP-BCSD and LP-non-BCSD was calculated using the Gray method. The subdistribution hazard ratio (SHR) of variables was estimated via the Fine and Gray proportional hazard regression model. Subgroup analyses for LP-BCSD and LP-non-BCSD were performed according to the HR status. Results: The risk of LP-BCSD was exceeded by that of LP-non-BCSD at > 5 years since the diagnosis, particularly in old women. The competing risk regression model indicated that hormone receptor-positive (HR+) was an independent factor for more LP-BCSD (hazard ratio, 1.54; 95% confidence interval, 1.44-1.54; p < 0.001). However, stratified analysis indicated that HR+ was only associated with more LP-BCSD in the young women subgroup. Although HR+ was associated with more LP-non-BCSD, the predictive value of HR+ for LP-non-BCSD was eliminated after adjusting for age. Conclusions: HR+ was related to LP-BCSD in the premenopausal population. LP-BCSD should be an optimal endpoint in future trials designed to evaluate the role of extended adjuvant endocrine therapy.