Current status of nanomedicine in the chemotherapy of breast cancer.

Despite the efforts that have been made in the field of breast cancer therapy, it is a leading cause of cancer death in women and a major health problem. The current treatments combine several strategies (surgery, radiotherapy, immunotherapy, hormone therapy, and chemotherapy) depending on cancer subtype and tumour stage. The use of chemotherapy is required in certain circumstances, like before or after surgery or in advanced stages of the disease. Chemotherapeutic regimens that include anthracyclines (e.g. doxorubicin), taxanes (e.g. paclitaxel), 5-fluorouracil and/or cyclophosphamide show, in general, a high toxicity that limit their clinical use. The use of targeted chemotherapy allows to get a selective location of the drug at tumour mass, decreasing the toxicity of these treatments. An increase of the antitumour efficacy can also be achieved. The use of nanocarriers containing anticancer drugs can be a good strategy to get targeted chemotherapy. In fact, several nanoformulations containing paclitaxel and doxorubicin have been approved or are under clinical trial for breast cancer therapy. The main advantage of these nanomedicines is their lower toxicity compared to conventional formulations, which can be attributed to the elimination of the solvents of the formulation (e.g. Cremophor-EL in paclitaxel conventional formulations) and the more selective location of the drug at tumour site (e.g. cardiotoxicity related to free doxorubicin). However, some adverse events (e.g. hand foot syndrome or infusion reactions) have been related to the administration of some nanomedicines, which have to be considered.