Introduction

The prevalence of breast cancer is increasing year on year as the incidence continues to rise and mortality decreases. The vast majority of women diagnosed with breast cancer in the UK can expect to survive the disease. This is partly a result of the success of early breast cancer screening, but also because of the widespread application of adjuvant therapy. Systemic treatment, incorporating chemotherapy, hormonal, and biological approaches, has successfully reduced the risks of tumor recurrence and death from metastatic breast cancer. That a proportion of patients relapse after definitive surgery and radiotherapy for early-stage localized disease, implicitly proves the presence of microscopic metastases, which are often present yet undetectable by current imaging methods. Adjuvant systemic therapy administered early in the cancer treatment algorithm eradicates micrometastases for many patients.

Collaborative randomized clinical trials of adjuvant therapy, involving many thousands of patients, have resulted in the incorporation of more effective cytotoxic agents into chemotherapy regimens and the optimization of administration schedules of these regimens, thus improving survival. Better understanding of the molecular events underlying breast cancer biology and metastasis, coupled with the rational introduction of targeted therapy, is leading toward more individualized treatment strategies. While these advances give much cause for optimism many challenges remain. One quarter of patients with early-stage breast cancer may develop recurrent disease. There remains a critical need to identify those women at high risk of recurrence and choose the therapy to which they are most likely to respond.