The Effect of Estrogen Receptor Status on Survival in Breast Cancer Patients in Ethiopia. Retrospective Cohort Study

BACKGROUND: There is wide global variance in survival from breast cancer, both in developed and developing country. However, the effect of estrogen receptor status has not been widely evaluated in Ethiopia where the incidence of breast cancer is rapidly increasing. Hence, the current study aimed to determine the effect of estrogen receptor status on the overall survival of breast cancer patients who were treated at Black Lion Specialized Hospital, Ethiopia. METHODS: In this institution-based retrospective cohort study a total of 368 study participants were included with a one-to-one ratio of estrogen receptor negative to estrogen receptor positive. The main outcome of interest for this study was death due to breast cancer. The authors compared the women with estrogen receptor-positive and estrogen receptor-negative breast cancer for overall survival rate using log rank test. The incidence density rate of mortality was calculated for each exposed and non-exposed variable. The effect of estrogen receptor status on breast cancer mortality was estimated using the Cox proportional hazards model. RESULTS: The incidence density rate of mortality among breast cancer patients for estrogen receptor positive were found to be 5.48 (95% CI=3.94–7.64) per 1,000 person years observation; while for estrogen negative receptor status the mortality rate was found to be 10.47 (95% CI=8.19–13.37) per 1,000 person years observation. In the Cox regression analysis after ful adjustments for confounder variables, the mortality event risk was 32% higher among estrogen receptor negative (HR=1.32; 95% CI=1.08–2.91) as compared to estrogen receptor positive breast cancer patients. CONCLUSION: We have found that the incidence density rate of mortality among breast cancer patients was significantly higher in the estrogen receptor negative groups. Therefore, clinicians should give careful attention to the impact of estrogen receptor negative status on the overall outcome of clients.