Prognostic significance of tumor subtypes in women with breast cancer according to stage: A population-based study.

Abstract

1070 Background: Tumor subtypes (TS) are an important prognostic tool in breast cancer patients (pts). However, with contemporary therapies the prognosis of different subtypes is unclear. Recently, the AJCC proposed to incorporate TS among other variables in the 8th edition of the staging manual. The aim of this study was to analyze differences in overall survival (OS) by TS according to stage compared with other factors. Methods: We evaluated women with microscopically confirmed invasive breast cancer between 2010 and 2013 with known estrogen receptor (ER) and progesterone receptor (PR) (together hormone receptor [HR]) status and human epidermal growth factor receptor 2 (HER2) status reported to the SEER program. Pts with other primary either before or after breast cancer were excluded. Pt characteristics were compared between TS. Univariate and multivariate analyses were performed to determine the effect of each variable on OS. Results: We included 166,054 pts. Median age was 60 years (range 18-108). Median follow-up was 21 months (range 1-48). TS distribution was: 72.5% HR+/HER2-, 10.8% HR+/HER2+, 4.8% HR-/HER2+ and 12% triple negative (TN). Pts with HR+/HER2- tumors were older, had lower grade and presented with earlier stage (all p < 0.0001). OS at 3 years for each subtype according to stage is shown in the table (p for interaction < 0.0001). These differences in OS by TS continued to be significant for each stage in multivariate analysis adjusted for age, race, grade, histology and marital status. Conclusions: In this cohort, we observed significant differences in pt characteristics according to TS. Although HR+/HER2- tumors had better clinicopathologic features, the HR+/HER2+ group had the best OS in most stages. OS was significantly different by TS in each of the 4 stages and these results remained significant in the multivariate model. Pts with TN stage 1 tumors had similar OS as pts with HR+/HER2+ stage 2 tumors. Our results support the incorporation of TS as part of the staging variables in breast cancer. [Table: see text]