Breast Cancer Survival Analysis Based on Immunohistochemistry Subtypes (ER/PR/HER2): a Retrospective Cohort Study.

BACKGROUND: We conducted this study to estimate the prevalence of biomarkers, including estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2 (HER2) among patients with breast cancer and to explore their effects on disease mortality.

METHODS: We conducted this registry-based retrospective cohort study in Tehran, in 2014, using the data on 1622 patients with breast cancer, diagnosed pathologically and registered with the Comprehensive Cancer Control Center from 1998 to 2013. The outcome of interest was the survival probability of patients with breast cancer based on receptor status along with other prognostic factors such as age, histopathology, stage/grade of tumor, metastatic status, and surgical procedures using the life table, Kaplan-Meier curves, and multivariate Cox proportional hazard model. We generated different subtypes based on expression of ER, PR, and HER2, positive (+) and/or negative (-).

RESULTS: ER+/PR+/HER2- subtype (51.5%) was the most common form of breast cancer cells. Compared to the ER+/PR+/HER- subtype, the hazard ratio (95% confidence interval) of cancer mortality was 2.14 (1.13, 4.03) for ER-/PR-/HER2- subtype, 1.92 (1.03, 3.59) for ER-/PR-/HER2+ subtype and 5.19 (1.51, 17.86) for ER-/PR+/HER2+ subtype.

CONCLUSION: In this study, breast cancer cases with ER-/HER2+ tumors had shorter survival than those with ER+/PR+/HER2- tumors. Triple negative tumors were the only other subtype with a statistically significant poorer prognosis. The results of this study in a middle-income country further indicate the importance of receptor status, in particular HER2 status, in the prognosis of breast cancer.