Utility of gene expression signature in treatment decision of breast cancer

Breast cancer is the most common cancer and a leading cause of cancer-related mortality in women worldwide. About 1.7 million women were diagnosed with breast cancer in 2012 and 6.3 million women were alive with breast cancer in the previous five years (1,2). Despite modern therapeutic interventions, the 5-year survival rate of breast cancer has improved only marginally and its recurrence is observed in more than 50% of the patients (3,4). Treatment failure and recurrence of breast cancer can be attributed to multiple factors which are difficult to predict for a particular patient (5). Genomic tests such as Oncotype DX, MammaPrint, miRNAs and other molecular and clinico-pathological markers are often employed for guiding therapeutic decisions (6-13) but it is difficult to say which test is reliable. Subtyping of breast cancer is largely based on estrogen/progesterone receptor (ER/PR), and human epidermal growth factor receptor 2 (HER2)/neu status and the most aggressive form is considered to be triple negative breast cancer (TNBC) (14), the drug resistance and recurrence rate of which is extremely high (15-17). Most alarmingly, TNBC has recently been found to be prevalent in as high as 74% of premenopausal women below 35 year of age (18). However, there exists no TNBC-specific therapeutic target yet.