OBJECTIVE: We retrospectively analyzed the clinical prognostic value of the 8th edition of the American Joint Committee on Cancer (AJCC) staging system for luminal A breast cancer. METHODS: Using both the anatomic and prognostic staging in the 8th edition of AJCC cancer staging system, we restaged patients with luminal A breast cancer treated at the Breast Disease Center, Peking University First Hospital from 2008 to 2014. Follow-up data including 5-year disease free survival (DFS), overall survival (OS) and other clinic-pathological data were collected to analyze the differences between the two staging subgroups. RESULTS: This study included 421 patients with luminal A breast cancer (median follow-up, 61 months). The 5-year DFS and OS rates were 98.3% and 99.3%, respectively. Significant differences in 5-year DFS but not OS were observed between different anatomic disease stages. Significant differences were observed in both 5-year DFS and OS between different prognostic stages. Application of the prognostic staging system resulted in assignment of 175 of 421 patients (41.6%) to a different group compared to their original anatomic stages. In total, 102 of 103 patients with anatomic stage IIA changed to prognostic stage IB, and 24 of 52 patients with anatomic stage IIB changed to prognostic stage IB, while 1 changed to prognostic stage IIIB. Twenty-two of 33 patients with anatomic stage IIIA were down-staged to IIA when staged by prognostic staging system, and the other 11 patients were down-staged to IIB. Two patients with anatomic stage IIIB were down-staged to IIIA. Among seven patients with anatomic stage IIIC cancer, two were down-staged to IIIA and four were down-staged to stage IIIB. CONCLUSIONS: The 8th edition of AJCC prognostic staging system is an important supplement to the breast cancer staging system. More clinical trials are needed to prove its ability to guide selection of proper systemic therapy and predict prognosis of breast cancer.