Background: Few studies have been undertaken to evaluate the prognostic value of age at diagnosis for determining breast cancer survival in a large population.
Methods: Using the U.S. National Cancer Institute's Surveillance, Epidemiology, and End Results (SEER) database consisting of 18 population-based cancer registries, this study identified 331,969 female patients with a diagnosis of breast cancer from 1 January 1990, to 31 December 31. Breast cancer-specific mortality (BCSM) was compared among patients in different age groups using Kaplan-Meier plots. The Cox proportional hazards model was used for multivariate analysis.
Results: In the multivariate analysis, the hazard ratios (HRs) of BCSM in the different age groups formed a U-shaped curve, with patients younger than 30 years and patients older than 79 years experiencing the worst survival rates (HR, 1.19; 95 % confidence interval [CI], 1.06-1.33; P = 0.003 and HR, 2.16; 95 % CI, 2.05-2.27; P < 0.001, with age 50-59 years as the reference, respectively). When the interaction between age at diagnosis and hormone receptor (HoR) status for prediction of BCSM was further analyzed, the findings showed that in the HoR-positive group, patients younger than 30 years and patients older than 79 years had the worst survival rates (HR, 1.52; 95 % CI, 1.30-1.76; P < 0.001 and HR, 2.07; 95 % CI, 1.94-2.20; P < 0.001, respectively), whereas patients ages 40 to 49 years had the best survival rate (HR, 0.93; 95 % CI, 0.89-0.98; P = 0.005). This pattern, however, was different in the HoR-negative group. Patients younger than 60 years had nearly the same BCSM (P = 0.356, 0.199, and 0.036 for ages <30 years, 30-39 years, and 40-49 years, respectively), with BCSM starting to increase with age only for patients older than 60 years and peaking for patients older than 79 years (HR, 2.39; 95 % CI, 2.20-2.59; P < 0.001).
Conclusions: The study findings show different patterns in the prognostic value of age for determining BCSM, depending on the HoR status. These data underscore the importance of age-specific studies for different HoR groups to individualize treatment and improve outcomes for breast cancer patients.