The different prognostic impact of age according to individual molecular subtypes in breast cancer

PURPOSE: Young age at diagnosis has been considered a poor prognostic factor. However, considering young age itself as an independent poor prognostic factor for all breast cancers is unwarranted. We analyzed the different prognostic effects of age as a prognostic factor according to molecular subtype. METHODS: We retrieved data from 1,819 patients with primary breast cancer at the breast cancer center between 2007 and 2012. We classified each molecular subtype in 3 age cohorts (<40, 40–50, and >50 years). The associations of age and molecular subtypes with relapse-free survival (RFS) and disease-specific survival (DSS) were assessed. RESULTS: Patients aged <40 years showed a poor histologic grade, hormone receptor negative expression than older patients, and had a higher proportion of triple-negative breast cancer (TNBC) (P < 0.001). This was thought to have led to a significantly shorter RFS than that of older patients (P < 0.001). In the subgroup analysis according to molecular subtypes, the poorer RFS was observed only in patients aged <40 years with luminal type breast cancer (P < 0.001). Age was an independent prognostic factor of RFS in luminal-type breast cancer (P = 0.001). However, no difference in RFS between age groups was found for patients with other subtypes (human epidermal growth factor receptor 2 overexpression, TNBC). No significant effect between age groups was found in DSS for patients with all molecular subtypes. CONCLUSION: Age at diagnosis of breast cancer affected prognosis differently according to molecular subtype. Age itself is not an independent prognostic factor. Age of <40 years showed a limited worse prognostic impact of recurrence in luminal type breast cancer only.