Surgery and radiation treat breast cancer in the breast and axilla. Systemic therapy treats breast cancer cells that cannot be treated by surgery or radiation, as well as treating breast cancer in the breast and axilla. The goal of systemic therapy, which gives medication via the bloodstream, is to treat the whole body.
Systemic therapy is most often given in the “adjuvant” setting (in other words, after surgery has been performed) to decrease the risk of the cancer returning. Your doctor will decide whether you need adjuvant systemic therapy and the type of therapy needed based on the size of the tumor, whether or not it has spread to lymph nodes, the tumor marker profile of your cancer (your cancer’s biology), and possibly genomic testing of your tumor (your cancer’s DNA).
Systemic therapy can also be given “neoadjuvantly,” meaning before surgery. Neoadjuvant therapy is recommended if a cancer is too large to be removed by surgery, in hopes of shrinking the cancer so that it can be surgically removed or, in some cases, to enable a lumpectomy to be performed instead of a mastectomy.
Systemic therapy is also given to patients whose cancer has recurred or spread to other organs. Once a breast cancer has metastasized outside of the breast and axilla, surgery plays a very small role in treatment and systemic therapy is used to kill or control the growth of the cancer.
Three different types of systemic therapies are used to treat breast cancer:
