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Background

The aim of this study is to evaluate the association between different treatments and survival time of breast cancer patients using either standard Cox model or stratified Cox model.

Methods

The study was conducted on 15830 women diagnosed with breast cancer in British Columbia, Canada. They were divided into eight groups according to patients’ ages and stage of disease Either Cox’s PH model or stratified Cox model was fitted to each group according to the PH assumption and tested using Schoenfeld residuals.

Results

The data show that in the group of patients under age 50 years old and over age 50 with stage I cancer, the highest hazard was related to radiotherapy (HR= 3.15, CI: 1.85-5.35) and chemotherapy (HR= 3, CI: 2.29-3.93) respectively. For both groups of patients with stage II cancer, the highest risk was related to radiotherapy (HR= 3.02, CI: 2.26-4.03)(HR= 2.16, CI: 1.85-2.52). For both …