A study of correlation between molecular subtypes of breast cancer and site of metastasis

Context: Studies have correlated the presence or absence of estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2 (Her2/neu) with metastatic spread and ultimate clinical outcomes in breast cancer. However, the influence of molecular subtype on the pattern of disease spread is not well known. Aims: The aim of this study is to evaluate the role of various molecular subtypes as a predictor of metastatic distribution in breast carcinoma. Settings and Design: This was a prospective observational study. Subjects and Methods: One-hundred and ten patients of infiltrating ductal carcinoma of breast with distant metastasis were included in the study. Evaluation for metastasis was done using radiodiagnostics. Pathological data were obtained from previous mastectomy specimens. Tumor marker status (ER, PR, and Her2/neu) was assessed, and patients were classified into Luminal A, Luminal B, Her2 enriched, and triple negative. Chi-square test was used to check the relationship between metastasis and different molecular subtypes (P < 0.05 was considered statistically significant). Statistical Analysis Used: Chi-square test was performed. Results: About 44.6% cases were Luminal A, followed by Luminal B (26.4%), triple negative (18.2%), and Her2 enriched (10.9%). Metastasis was seen in bones (62.7%), lungs (38.2%), liver (27.3%), and brain (10.9%). Luminal A breast cancers metastasized most commonly to bones (71.4%), lungs (36.7%), liver (18.4%), and brain (8.2%) (P = 0.0001). Luminal B type spread to bones in 62.1% cases, followed by liver (37.9%), lungs (34.5%), and brain (10.3%) (P = 0.001). Triple negative type cancers involved bones (60%), lungs (50%), liver (20%), and brain (10%) (P = 0.002). Her2-enriched cancers spread to liver (50%), followed by bones and lungs (33.3% each) and brain (25%) (P = 0.630). Conclusions: The major molecular subtypes in breast cancer are evidently different with regard to their ability to metastasize to different organs.