Prognostic significance of young age (<35 years) by subtype based on ER, PR, and HER2 status in breast cancer: a nationwide registry-based study

Abstract

Background: Young age is regarded as an adverse prognostic factor in patients with breast cancer, especially in those with a hormone receptor (HR)-positive tumor. We investigated the prognostic significance of an age of <35 years stratified by molecular subtype based on HR and HER2.

Methods: Two large databases of Korean breast cancer patients, which included nationwide registry data, were analyzed.

Results: In an analysis of 2,474 patients from the single institution, an age of <35 years was found to be an independent predictor of recurrence in patients with HR+/HER2- (hazard ratio 1.87; 95% confidence interval [CI]: 1.11-3.14; P=0.018), HR+/HER2+ (hazard ratio 3.09; 95% CI: 1.19-8.03; P=0.020), and HR-/HER2+ (hazard ratio 2.01; 95% CI: 1.03-3.92; P=0.040) subtypes, but not in those with the HR-/HER2- (triple-negative, TN) subtype (hazard ratio 1.08; 95% CI: 0.60-1.95; P=0.802). The results of an analysis of nationwide database data on 31,672 patients also showed that an age of <35 years significantly predicted poor cancer-specific survival in patients with HR+/HER2- (hazard ratio 3.40; 95% CI: 2.41-4.82; P<0.001), HR+/HER2+ (hazard ratio 1.96; 95% CI: 1.23-3.12; P=0.005), and HR-/HER2+ (hazard ratio 1.65; 95% CI: 1.07-2.52; P=0.022) subtypes, but again not in those with the TN subtype (hazard ratio 1.21; 95% CI: 0.88-1.67; P=0.240).

Conclusion: The prognostic significance of young age was found to depend on molecular subtype. An age of <35 years was a poor prognosticator in patients with the HR+/HER2-, HR+/HER2+, and HR-/HER2+ subtypes, but not in those with the TN subtype.