In many cases additional treatment is required after surgery. This is called adjuvant therapy. The adjuvant treatment for breast cancer may include chemotherapy, hormonal therapy, radiotherapy or immunological therapy. Usually a combination of the above is administered. The objective of adjuvant treatment is to destroy residual cancer cells circulating in the body, preventing them from lodging in organs and giving rise to distant metastases. Currently there are no means to identify these circulating cancer cells, but based on a number of the characteristics of breast cancer the probability of recurrence or metastases can be estimated. From large international clinical studies, we know that chemotherapy and hormonal therapy can reduce the risk of relapse and death from breast cancer by 30-40%.