Objective  To retrospectively evaluate the prognostic risk factors of T1-2 stage breast cancer patients with one to three positive node(s) and their effects on the benefits of post-mastectomy radiation therapy (PMRT).

  Methods   We retrospectively analyzed 457 breast cancer patients with T1-2 stage and one to three positive axillary lymph nodes treated in our hospital between 2000 and 2002. The independent prognostic factors of the patients were calculated by the Cox proportional hazards model. The patients were further classified into high-risk and low-risk subgroups according to the risk factors to explore the benefit of PMRT on the prognosis of different subgroups using survival analysis.

  Results   PMRT was not an independent beneficial factor of overall survival (OS) (HR=0.949; CI: 0.435-2.074; P=0.896) or loco-regional recurrent free survival (LRRFS) (HR=0.611; CI: 0.231-1.614; P=0.320) in all patients. Extracapsular extension (ECE) and pathological grades were independent prognostic risk factors, and the benefits of PMRT were significantly different on the prognosis of high-risk subgroup patients (group ECE+OS: P=0.020, LRRFS: P=0.014; group Grade Ⅲ OS: P= 0.002, LRRFS: P < 0.001). Meanwhile, PMRT failed to prolong the OS and LRRFS of low-risk subgroup patients (group ECE+OS: P= 0.353, LRRFS: P=0.796; group Grade Ⅰ to Ⅱ OS: P=0.267, LRRFS: P=0.589).

  Conclusion   ECE and grade Ⅲ were the independentrisk factors of death and loco-regional recurrence in the T1-2 breast cancer patients with one to three positive lymph node(s). PMRT was an effective adjuvant therapy to improve the prognosis of patients with high-risk factors. However, the benefit of PMRT had no significance in patients with ECE- or grade Ⅰ-Ⅱ.