A patient's treatment options depend on a number of factors. These factors include her age and menopausal status; her general health; the size, location, and stage of the tumor; whether the doctor can feel lymph nodes under her arm; and the size of her breast. Certain features of the tumor cells (such as whether they depend on hormones to grow) are also considered. The most important factor is the stage of the disease. The stage is based on the size of the tumor and whether the cancer has spread. The following section contains brief descriptions of the stages of breast cancer and the treatments most often used for each stage. (Other treatments may sometimes be appropriate.)

Stage 0 is sometimes called noninvasive carcinoma or carcinoma in situ.
Lobular carcinoma in situ, or LCIS, refers to abnormal cells in the lining of a lobule. These abnormal cells seldom become invasive cancer. However, their presence is a sign that a woman has an increased risk of developing breast cancer. This risk of cancer is increased for both breasts. Some women with LCIS may choose to take a medication called tamoxifen to try to prevent breast cancer, or they may take part in studies of other promising new preventive treatments. Others may not receive any treatment, but return to the doctor regularly for checkups. Still others may have surgery to remove both breasts to try to prevent cancer from developing. (In most cases, removal of underarm lymph nodes is not necessary.)

Ductal carcinoma in situ, also called intraductal carcinoma or DCIS, refers to cancer cells in an area of abnormal tissue in the lining of a duct that have not invaded the surrounding breast tissue. If DCIS lesions are left untreated, over time cancer cells may break through the duct and spread to nearby tissue, becoming an invasive breast cancer. Patients with DCIS may have a mastectomy or may have breast-sparing surgery followed by radiation therapy. Underarm lymph nodes are not usually removed. Women with DCIS may want to talk with their doctors about the possible usefulness of treatment with tamoxifen.

Stage I and stage II are early stages of breast cancer, but the cancer has invaded nearby tissue. Stage I means that cancer cells have not spread beyond the breast and the tumor is no more than about an inch across. Stage II means one of the following: the tumor in the breast is less than 1 inch across and the cancer has spread to the lymph nodes under the arm; the tumor is between 1 and 2 inches with or without spread to the lymph nodes under the arm; or the tumor is larger than 2 inches but has not spread to the lymph nodes under the arm.

Women with early stage breast cancer may have breast-sparing surgery followed by radiation therapy as their primary local treatment, or they may have a mastectomy, with or without breast reconstruction (plastic surgery) to rebuild the breast. Sometimes radiation therapy is also given to the chest wall after mastectomy. These approaches are equally effective in treating early stage breast cancer. The choice of breast-sparing surgery or mastectomy depends mostly on the size and location of the tumor, the size of the woman's breast, certain features of the cancer, and how the woman feels about preserving her breast. With either approach, lymph nodes under the arm usually are removed.

Many women with stage I and most with stage II breast cancer have chemotherapy and/or hormonal therapy in addition to surgery or surgery and radiation therapy. This added treatment is called adjuvant therapy. It is given to try to destroy any remaining cancer cells and prevent the cancer from recurring, or coming back.

Stage III is also called locally advanced cancer. The tumor in the breast is large (more than 2 inches across), the cancer is extensive in the underarm lymph nodes, or it has spread to other lymph nodes or tissues near the breast. Inflammatory breast cancer is a type of locally advanced breast cancer.

Patients with stage III breast cancer usually have both local treatment to remove or destroy the cancer in the breast and systemic treatment to stop the disease from spreading. The local treatment may be surgery and/or radiation therapy to the breast and underarm. The systemic treatment may be chemotherapy, hormonal therapy, or both; it may be given before or after the local treatment.

Stage IV is metastatic cancer. The cancer has spread from the breast to other parts of the body.

Women who have stage IV breast cancer receive chemotherapy and/or hormonal therapy to destroy cancer cells and control the disease. They may have surgery or radiation therapy to control the cancer in the breast. Radiation may also be useful to control tumors in other parts of the body.

Recurrent cancer means the disease has come back in spite of the initial treatment. Even when a tumor in the breast seems to have been completely removed or destroyed, the disease sometimes returns because undetected cancer cells remained in the area after treatment or because the disease had already spread before treatment. Most recurrences appear within the first 2 or 3 years after treatment, but breast cancer can recur many years later. Cancer that returns only in the area of the surgery is called a local recurrence. If the disease returns in another part of the body, it is called metastatic breast cancer. The patient may have one type of treatment or a combination of treatments.