Mechanisms and consequences of chemotherapy resistance in breast cancer

Resistance to chemotherapy is a substantial clinical problem limiting the effectiveness of anticancer drug treatment. Resistance accounts for treatment failure in more than 90% of patients with metastatic disease. Overcoming mechanisms of resistance is crucial for the effective management of breast cancer, particularly once the disease has metastasised. However, approaches to reverse multi-drug resistance (MDR) have so far met with limited success. Targeted therapies are now well established in the clinic. Developmental agents with improved specificity for tumour cells also show promise. In addition, novel cytotoxics such as the epothilones, which have low susceptibility to some of the common types of drug resistance and have demonstrated activity in taxane-resistant breast cancer, also show promise. We are now in a new era for cancer therapeutics where there are increasing treatment options for oncology patients. There is, therefore, some optimism for the improvement in the management and survival of patients with metastatic breast cancer.