context: Radiation therapy uses high levels of radiation to kill cancer cells or keep them from growing, dividing, or spreading to other body parts. Because it targets only the cancer cells, it causes less damage to nearby healthy cells. External beam radiation is most commonly used to treat breast cancer. A machine outside your body aims a beam of radiation on the area affected by the disease. Brachytherapy delivers radiation to the cancer through something implanted in your body. Proton therapy sends highly targeted radiation just to your breast tissue and not into your heart or lungs. Your doctor may recommend radiation: During surgery as a single dose at the site where the tumor was removed After a lumpectomy (a breast-conserving surgery to remove a tumor) or after a mastectomy to lower the odds of the cancer returning in that breast To treat some symptoms of advanced cancer Treatments generally start several weeks after surgery so your body has some time to heal. If your doctor recommends chemotherapy, too, you might start chemo first. You'll have small marks and stickers placed on your skin along the treatment area to give your medical team a map to follow. Don't try to wash these marks off or retouch them if they fade; the therapist will re-mark them when needed. When you go for a treatment, your therapist will escort you into the room and help you get in the right position. Then she'll leave and start the treatment. It's important to hold still and stay relaxed. Cameras and an intercom allow the therapist to see and hear you. Tell her right away if you're concerned about something. The therapist will be in and out of the room to reposition the machine and your body. The machine won't touch you, and the treatment itself won't hurt. This is a type of external beam radiation that uses energy from positively charged particles called protons to damage the DNA in cancer cells so they can no longer divide or grow. You usually get it 4 to 6 weeks after surgery or chemotherapy, and you'll get it 5 days a week for several weeks for 30-45 minutes a day. Depending on the dose and type, you may notice these during treatment: Red, swollen, warm, sensitive skin -- it might feel like you have a sunburn. It may peel or become moist and tender. Hair loss Less sweat where you were treated Fatigue Breast swelling Changes in skin sensation These side effects usually go away gradually within 4 to 6 weeks after your last treatment. Tell your doctor or nurse if you see skin changes outside the treated area. Long-term side effects can last beyond a year after treatment. They may include: A slight darkening of your skin Enlarged pores on your breast More sensitive or less sensitive skin Thickening of breast tissue or skin A change in the size of your breast These complications are rare: Broken ribs Heart damage Inflamed lung tissue Lymphedema (swelling, usually in the arm) if you had lymph nodes removed Secondary or new cancer or tumor Sore chest wall These steps can help: Gently cleanse the treated area using lukewarm water and a mild soap. Don't rub your skin. Pat it dry with a soft towel, or use a hair dryer on a cool setting. Don't scratch or rub the treated area. Use only an electric razor if you need to shave there. Don't put on medical tape or bandages. Don't apply any ointment, cream, lotion, or powder to the treated area unless your doctor or nurse has prescribed it. This includes cosmetics, shaving lotions, perfumes, and deodorants. Choose clothes made from natural fibers like cotton rather than tight-fitting clothing or harsh fabrics like wool or corduroy. Avoid extreme heat or cold where you've had radiation -- no electric heating pads, hot water bottles, or ice packs. Stay out of direct sunlight, especially between the hours of 10 a.m. and 2 p.m., even after you're done with treatment. The sun can intensify skin reactions and lead to severe sunburn. Choose a sunscreen of SPF 30 or higher. Wear protective clothing, such as a long-sleeved shirt, pants, and a wide-brimmed hat, too. Radioactive seeds or pellets as small as grains of rice are placed inside the breast, near the cancer. Whether this treatment might be right for you will depend on your tumor's size, location, and other things. Brachytherapy can be used alone or with external beam radiation. Most people have reactions like: Redness Bruising Breast pain Less likely, but still possible, problems include: Infection Damage to fatty tissue in the breast Weakness and fracture of the ribs in rare cases Fluid collecting in the breast (seroma) Radiation affects each person differently. To help keep your energy up during radiation treatments: Get enough rest. Eat a well-balanced, nutritious diet. Pace yourself, and plan frequent rest periods. Good nutrition will also help you recover from side effects, heal, and fight off infection. It may give you a sense of well-being, too. If you have a hard time eating, work with a dietitian to find ways to get the nutrients you need. Many people feel fatigued after several weeks of treatment. Most often, this is mild. But some people feel more tired and may need to change their daily routines. Your doctor will let you know if they think you should limit your activities. You'll see your doctor for follow-up exams and X-rays. They'll tell you how often to come in.