Resistance to Chemotherapy in Breast Cancer

Breast cancer (BC) is the most frequently diagnosed cancer in women and the leading cause of death for women worldwide. Conventional clinical treatment of BC entails surgery, radiation therapy, hormone therapy, chemotherapy (CT), and targeted therapies. CT plays a critical role in cancer treatment and is linked with improved prognosis in BC patients. However, tumors can become resistant to CT which results in recurrence, treatment failure, and mortality. The underlying mechanisms of chemoresistance in BC are not fully elucidated. This is due to the heterogeneous nature of this disease and the wide spectrum of CT regimens used. Furthermore, current treatment strategies to overcome chemoresistance showed limited success. Therefore, novel and efficacious strategies are urgently needed to overcome chemoresistance in BC. This review sheds light on various mechanisms underlying chemoresistance in BC, including genetic factors, cancer stem cells, and drug efflux. Novel strategies that can be used to combat chemoresistance in BC are also discussed. Novel drug delivery methods, gene therapy, and combining CT with other therapeutic strategies like immunotherapy are some of them. We highlight that further understanding the mechanisms involved in BC chemoresistance can help to develop novel and efficacious treatment strategies and ameliorate current strategies to overcome chemoresistance.