New therapeutic approaches in breast cancer.

Breast cancer is the most common cancer among women in the UK, with 46,000 new cases and 12,000 deaths due to this disease estimated to have occurred in 2008. Around three-quarters of breast cancers express the estrogen receptor and are therefore presumed to be hormone-responsive and potentially treatable or preventable by anti-estrogenic agents. Expression of the HER2 receptor occurs in a fifth of breast cancers and is associated with limited endocrine response in hormone receptor-positive tumours and directs treatment with HER2-targeted agents. Despite improvements in the clinical outcome of breast cancer patients through the development of endocrine and targeted agents, overcoming de novo or acquired resistance remains a considerable therapeutic hurdle. In addition, as our understanding of the complexity of breast cancer biology increases, it is clear that existing therapies will fall short of offering an effective treatment solution to many patients. The ability to profile molecular pathways in drug-responsive and drug-resistant tumours has provided an important step in identifying novel targets in breast cancer. To this end, a number of new targeted therapeutics are currently being investigated both as single agents and as a means to improve existing therapeutic regimens.