Association of Estrogen Receptor, Progesterone Receptor, and Human Epidermal Growth Factor Receptor 2 Expression with Breast Cancer Metastasis in Iran

BACKGROUND: Metastasis is an important factor in the survival estimate of patients with breast cancer. The present study aimed to examine the frequency of epidermal growth factor receptor 2 (HER2), estrogen receptor (ER), and progesterone receptor (PR) expression in relation to the metastatic site, pattern, and tumor size in patients with metastatic breast cancer (MBC). METHODS: In this retrospective study, the medical records of patients diagnosed with MBC at Motahari Clinic (Shiraz, Iran) during 2017-2019 were examined. Metastasis was confirmed using computed tomography, and a total of 276 patients were included in the study. Based on the expression of receptors, the patients were categorized into luminal A, luminal B, HER2, and TNBC groups. The frequency and percentage of receptors in relation to the metastatic site, size, and pattern were compared using the Chi square test. P<0.05 was considered statistically significant. RESULTS: The frequency of receptor positivity in the 276 selected medical records were of the subtype HER2-enriched (n=48), luminal A (n=43), luminal B (n=146), and TNBC (n=39). The most common metastatic sites were the bones (47.1%), lungs (34.4%), liver (27.9%), brain (20.3%), and other organs (12.7%). The first site of metastasis occurred in the bones (36.6%), lungs (17.4%), liver (15.6%), brain (10.5%), and other organs (7.6%). The frequency of receptor expression was different in relation to the first metastatic site (P=0.024). There was a statistically significant difference between the frequency of receptor expression in patients with bone (P=0.036), brain (P=0.031), and lung (P=0.020) metastases. The frequency of receptor expression was also significantly different in relation to the size of liver metastasis (P=0.009). Luminal A and B subtypes showed higher rates of bone metastasis as the first metastatic site. CONCLUSION: The difference in the frequency of receptor expression in relation to the metastatic site and tumor size can be used as predictive and prognostic factors in patients with breast cancer.