The prognostic value of age for invasive lobular breast cancer depending on estrogen receptor and progesterone receptordefined subtypes: A NCDB analysis

Purpose: We aimed to assess the effect of age on survival according to estrogen receptor (ER) and progesterone receptor (PR)-defined lobular breast cancer subtype in a wide age range. Methods: 43,230 invasive lobular breast cancer women without comorbidities diagnosed between 2004 and 2011 in the National Cancer Database (NCDB) were analyzed. The effects of age on overall survival (OS) among different age groups were evaluated by log-rank test and Cox proportional model. Results: Multivariate analysis showed that patients diagnosed at both young (<35 years) and old (≥70 years) ages had worse prognosis compared with those in the middle ages. We further analyzed the interaction between age and molecular subtype for predicting OS: in ER+PR+ subtype, the HR of OS declined with age from 1.55 (95% CI, 1.08-2.22; P = 0.019) in the group younger than 35 years to 1.38 (1.02-1.86; P = 0.036) in the 35-39 group, but increased with age to 10.1 (8.49-11.94; P < 0.001) in the group older than 79. While in ER+PR- and ER-PR- subtypes, the HRs showed no statistical differences among women diagnosed before 60 (P > 0.1); and in ER-PR+ subgroup, the HRs were similar in patients younger than 70 (P > 0.1); thus, the plots of HRs in these three subtypes remained steady until the age of 60 or 70. Conclusions: Our findings identified that the effect of age on OS in lobular breast cancer varied with ER/PR-defined subtypes. Personalized treatment strategies should be developed to improve outcomes of breast cancer patients with different ages and ER/PR statuses.