Metastatic Trends in Breast Cancer According to Molecular Subtypes, Estrogen Receptor, Progesterone Receptor and Human Epidermal Growth Factor Receptor 2neu Status

Abstract

Background : Breast cancer molecular subtypes have been established a close relationship with site specific metastasis, disease prognosis, selection of therapy and response to therapy. This study is the evaluation of primary tumor molecular determinants and its clinical outcome in association with metastatic behavior of breast cancer. Material and Methods: This prospective study was included 221 patients of breast cancer registered in the department between January 2016 to December 2018. Based upon hormonal status, patients with breast cancer were categorized into four groups i.e. luminal (ER+, PR+, HER 2neu-), HER 2neu enriched (ER-, PR-, HER 2neu+), triple positive (ER+, PR+, HER 2neu+) and triple negative (ER-, PR-, HER 2neu-). Metastatic sites were divided into skeleton and visceral (lung, liver, and brain). The study data was compiled using Microsoft Excel sheet and Chi-Square test was used to assess the association between categorical variables. P value less than 0.05 was considered as statistically significant. Results : The mean age of the patients was 48.21±11.4 years (ranging from 22 to 80 years). About 36.7% and 24.9% patients were diagnosed as stage III A and stage II B respectively. Majority of patients were categorized as luminal (43%), followed by 24%, 17.2% and 15.8% as triple negative, triple positive and HER 2neu enriched respectively. Metastasis to bone following breast cancer was observed in majority i.e. 11.8% cases. Lung and liver metastasis observed in 6.3% cases each whereas brain metastasis was observed in 0.9% cases only. The higher proportions of TNBC cases metastasized to bone (22.6%), liver (7.5%), lung (7.5%) and brain (1.9%). The association between metastasis and hormonal status was statistically highly significant for bone metastasis (p<0.05). Conclusion : Breast cancer molecular subtypes have been related to considerable distinction in pattern of distant spread. Bone is the most predominant site of metastases followed by liver lung and brain. Luminal and HER 2 neu enriched subtypes having greater propensity for visceral metastasis where as TNBC predominantly show bone metastasis in this study. Keywords: Breast cancer, molecular subtypes, site-specific metastasis