Age-dependent differences in survival of patients with early breast cancer: analysis of SUCCESS A, B, C trials

PURPOSE: Elderly breast cancer (BC) patients are commonly at risk of under-treatment, which can negatively affect their prognosis. Therefore, we analyzed age-related survival differences considering clinico-pathological parameters among patients with early BC. METHODS: 8190 BC patients from SUCCESS A, B, and C trials who underwent surgery and adjuvant systemic therapy were analyzed. Tumor and nodal stage, grading, biological subtype, types of surgical and systemic therapies, and other clinico-pathological parameters were compared between age groups ≤ 50 years, 51-65 years, > 65 years (chi-square tests). Breast cancer-free interval (BCFI), breast cancer-specific survival (BCSS), overall survival (OS), invasive disease-free survival (iDFS), and distant disease-free survival (DDFS) were analyzed using univariable and adjusted multivariable Cox regression models. Two-way interactions between age and other clinico-pathological parameters were calculated. RESULTS: There were significant differences between the age groups concerning almost all parameters analyzed, especially more advanced tumor stages in the elderly group. Univariable analysis showed significant differences between the age groups for all survival parameters (all p < 0.001). However, after adjustment for other prognostic parameters, an independent significant age effect was found only for iDFS (p = 0.038), while there was no significant independent age effect on BCFI (p = 0.286), BCSS (p = 0.981), OS (p = 0.131) and DDFS (p = 0.316). CONCLUSION: Although elderly BC patients > 65 years had poorer survival, multivariable analysis suggests this difference is mostly attributable to advanced tumor stages rather than age itself. Effective BC screening and research related to the influence of (biological) age on response to cancer therapies could be the next step to improve understanding the relationship between patient age and BC survival.