Prognosis by novel staging systems incorporating tumor biology in estrogen receptor positive and human epidermal growth factor receptor negative breast tumors

Abstract Purpose The prognostic stage group and Bioscore are novel staging systems for breast cancer patients. They provide a better view on five-year disease-specific survival (DSS) compared to the traditional staging system. Five-year follow-up might not be sufficient for ER+HER2- tumors. This study determines five- and 10-year recurrence-free survival (RFS) for the anatomic and prognostic stage group of the 8 th AJCC TNM and Bioscore staging system, and compares these systems for ER+HER2- breast cancer patients. Methods All newly diagnosed ER+HER2- breast cancer patients treated with primary surgery in 2005 were included from the Netherlands Cancer Registry with a ten-year follow-up. All patients were staged according to 8 th AJCC TNM (both anatomic and prognostic stage group) and the Bioscore staging system. Five- and 10-year RFS was compared using Kaplan-Meier analysis. The ability to discriminate groups was quantified by the concordance statistic (c-statistic). Results Five-year RFS ranged from 65.0-91.1% (anatomic) and from 40.9-91.8% (prognostic stage group). The Bioscore staging system ranged from 54.9-92.1%. Ten-year RFS rates were 52.9-84.9% (anatomic stage), 31.8-84.6% (prognostic stage) and 47.1-85.1% (Bioscore). All systems similarly discriminated groups with comparable c-statistic score (five- and 10-year 0.58-0.60). The prognostic stage group identified a group (IIIC) with very poor prognosis (31.8%) which could not be identified using the other staging systems (10-year RFS for 52.8% for anatomic IIIC and 47.1% for Bioscore 6). Conclusion All three staging systems similarly discriminated groups for ER+HER2- breast cancer patients with a five- and 10-year follow-up. However, the prognostic stage group showed a wider distribution of the 10-year RFS compared to anatomic stage group and Bioscore staging system.