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

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.

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.

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.

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.