Local treatments are those that destroy, remove, or control the breast cancer cells in a particular area. Surgery and radiation are both local treatments.
Systemic treatments are those that destroy the cancer cells throughout the body. Chemotherapy and hormonal therapy are both systemic treatments.
The stage of a cancer generally will determine which type of treatment is used. Often, breast cancers will undergo a combination of local and systemic treatments. For example, lumpectomy is almost always followed by a course of radiation therapy, because the cancer surgeon cannot be sure that all of the cancer cells were removed when the tumor was removed.
Sometimes, the surgery is the second part of the treatment. For example, some tumors are first treated with chemotherapy or hormonal therapy to suppress the ability of the cancer cells to proliferate. In this approach (called neoadjuvant therapy), once the cancer has shrunk, surgery usually follows.