Once surgery is complete, most women receive additional treatment, often referred to as adjuvant treatment. The term refers to the use of radiation, chemotherapy, or hormonal therapy after surgery to kill or inhibit any metastatic cancer cells that remain in the body. The goal of these therapies is to prevent recurrence.

Radiation is a local therapy directed at any remaining cancer cells in your breast or armpit. The radiation oncologist applies a powerful x-ray beam to the area of the tumor to kill any cancer cells left after surgery. Radiation is routinely used after breast-conservation surgery and may be used after mastectomy for more advanced cancers.

Infrequently, radiation may also be used as a neo­­adjuvant (presurgical) treatment to shrink the tumor, to make it possible to have a mastectomy so that there is less tissue to remove during the operation.

Chemotherapy is also used for this purpose.

Radiation therapy is a lot like having an x-ray, except that each treatment session takes about 10 minutes. The typical radiation therapy requires one treatment five days a week for slightly more than six weeks, although some newer, shorter regimens are being tested. Using many small daily doses of radiation rather than a few large doses helps protect normal tissues and produces a better long-term cosmetic result.

During the planning session before radiation therapy, your radiation team will take careful measurements to determine the precise angles for focusing the radiation beam into the target area (breast, chest wall, and armpit) while avoiding adjacent, underlying tissues, including the lungs and heart. Several pin-head dots that aid in focusing the beam will be tattooed around your breast. To minimize radiation damage to the front of the heart, particularly for patients with left-sided breast cancer, CT scan images may be taken.

Radiation treatment, like any x-ray, is painless. You lie on a special table while the machine circles around you. A form is constructed during the planning session to help you remain stationary for four or five minutes.

The doses of radiation that damage or destroy cancer cells also can injure or kill normal cells, leading to side effects. The most common side effect is fatigue, which comes on gradually over a period of weeks because your body burns a great deal of energy during this treatment. It's important not to fight it, but to get as much rest and sleep as your body craves. These sporadic feelings of weariness are likely to last for four to six weeks after the end of treatment. Other common reactions include swelling and heaviness in the breast and a sunburn effect, such as reddened or darkened skin in the treated area that may feel tender to the touch. Occasionally during treatment, the skin may blister, crack, or peel. Radiation of the axillary nodes under the arm can cause lymphedema. In rare instances, a patient's blood cell count will drop.

To manage these reactions, the nurse on your radiation team can suggest creams that help repair skin damage. In addition, you should be gentle with the entire treated area until it no longer feels sore. A bra may be uncomfortable, so try wearing soft, lightweight garments, such as a camisole or an old cotton T-shirt, instead. Exposure to the sun is likely to worsen the sunburn effect. You will need to cover the treated area with clothing or a sunscreen of SPF-15 or higher during and even years after the radiation treatment.

Other, longer-lasting reactions to radiation therapy may include an increased firmness or a slight shrinkage of the treated breast, which may occur months after treatment and may be lifelong. Infrequently, the breast may become swollen and remain that way for several years. Rare and long-lasting side effects are a significant increase in breast firmness, marked breast shrinkage, a change in color of the nipple and areola, rib fractures in the treated area, lung inflammation, and lung scarring (as radiation paths may include some ribs and part of the lung).

Partial breast irradiation. Because radiation therapy requires a large time commitment over a six-week period or more, researchers are looking at ways to reduce radiation treatment to just a few sessions during which a higher dose of radiation is focused more narrowly on the area of the tumor. Known as partial breast irradiation, the treatment is delivered by cath­eter (high-dose rate brachytherapy) or a balloon (balloon brachytherapy) placed around or in the site of the tumor. The treatment lasts just five days. In another approach, called intraoperative radiotherapy, a single dose of radiation is administered to the lump­ectomy site at the time of surgery.

Long-term survival rates and recurrence rates are not yet known for these techniques. Until more data are available, the American Society of Breast Sur­geons suggests that partial breast irradiation be performed only as part of a medical center protocol or multi-institutional trial.