Young age is an independent adverse prognostic factor in early stage breast cancer: a population-based study.

Objective: To compare the prognosis of young breast cancer patients with the older ones.

Patients and methods: Utilizing the Surveillance, Epidemiology, and End Results database, we identified 150,588 female breast cancer patients diagnosed during 2003-2014, including 6,668 patients younger than 35 years and 143,920 patients aged between 35 and 60 years. Kaplan- Meier analysis was performed to compare the prognosis of these two groups. Univariate and multivariate Cox proportional hazard models were utilized to identify independent prognostic factors and calculate the HR and 95% CI. Subgroup analysis was performed stratified according to the lymph node status and estrogen receptor (ER) status.

Results: The young patients presented with more aggressive clinicopathological characteristics, including larger tumor size ( P <0.001), more lymph node metastasis ( P <0.001), higher grade (grades III and IV, P <0.001), more ER/progesterone receptor absence ( P <0.001), and more human epidermal growth factor receptor 2 overexpression ( P <0.001). The patients younger than 35 years presented with inferior breast cancer-specific survival (BCSS) and overall survival (OS) (log-rank, P <0.001) in comparison with the older ones. In the multivariable Cox proportional hazard regression analysis, young age remained to be an independent adverse prognostic factor in operable breast cancer in terms of BCSS (HR, 1.200; 95% CI, 1.110-1.297; P <0.001) and OS (HR, 1.111; 95% CI, 1.032-1.196; P =0.005). In the subgroup analysis, young age remained a significant adverse prognostic factor in N0 (BCSS), N1, and ER-positive subgroups ( P <0.05).

Conclusion: Young age is an independent adverse prognostic factor in operable breast cancer. Young patients may receive more intensive treatment than older ones.