Background: Prognostic factors for survival of metastatic breast cancer (MBC) patients are important for identifying risks
and deciding on patient treatment; however, few studies of prognostic factors in MBC have been performed in Thailand.
Objective: To determine the survival duration and prognostic factors for overall survival in metastatic breast cancer.
Material and Method: This retrospective cohort study was conducted by reviewing 232 files of MBC patients treated in the
Oncology Unit, Department of Medicine, Rajavithi Hospital from January 1st 2005 to December 31th 2013.
Results: There were 232 patients whose median age was 51.5 years. The 1-year, 3-year and 5-year overall survival rates for
MBC patients were 53.2%, 18.7% and 7.3% respectively, and the median overall survival time of all MBC patients was 13.43
months. Multivariate analysis showed that large tumor size T4 (HR = 1.89, 95% CI 1.04-3.44; p = 0.038), ECOG performance
status 3-4 (HR = 2.44, 95% CI 1.48-4.00; p<0.001) and treatment with best supportive care only (HR = 5.95, 95% CI 3.56-9.96; p<0.001) were significant prognostic factors for poor overall survival in MBC. Breast cancer subtype analysis showed
that luminal-A subtype was associated with a high rate of late recurrence (beyond 2 years) (p = 0.016) and HER-2 enriched
subtype was related to a high rate of early relapse (before 2 years (p = 0.001)).
Conclusion: The important prognostic factors for overall survival in MBC were tumor size, ECOG PS and type of first-line
treatment. In order to improve survival outcomes, patients with large tumor size should be treated with intensive chemotherapy
and targeted therapy if HER-2 status positive. It is essential that early breast cancer patients have an awareness of recurrent
diseases in order to identify good performance status in MBC patients suitable for active treatment.

Keywords: Metastatic breast cancer, Survival, Prognostic factor