Radiation therapy remains one of the most common tools for breast cancer treatment, but it has been refined considerably over the years.

Radiation therapy comes in two basic types: internal or external.

External radiation treatments consist of an energetic, highly focused beam used to destroy cancer cells and surrounding tissue. Though the beam is invisible to the eye, it can pass semi-transparently through the skin. The different composition and behavior of the cancer cells, though, causes them to react differently.

Healthy cells are in the path of the radiation and are affected by it. But, as cancer cells are actively dividing and growing in abnormal ways, their function is more readily interrupted. They may absorb a much higher percentage of the radiative energy than healthy cells. That energy kills the cancer cells. The beam may also destroy the blood vessels around the tumor that the cancer generates in order to feed itself.

Internal radiation therapy, sometimes called brachytherapy, is more akin to chemotherapy. But rather than using drugs per se to affect a chemical change, a small amount of radioactive material is implanted. That material ejects radiation that targets cancer cells, killing them from the inside.

Internal radiation therapy is much less common. But, as with any treatment regimen, when and how it is used is determined after discussion with a specialist.

Radiation therapy is often used as a precursor or adjunct treatment, accompanying other methods. After a modified mastectomy, for example, an oncologist may recommend a course of radiation treatments lasting six to eight weeks.

The goal is to ensure that any cancerous cells the surgeon couldn't remove are destroyed by the radiation. But it's a less intensive treatment since using radiation to kill the entire cancer would involve higher and longer doses.

Similarly, radiation treatments may accompany chemotherapy. Since each case is unique, the patient and oncologist will determine what's best for each person. In other cases, it may be used solely to relieve symptoms without any expectation of cure.

Despite the high energy in the beam, radiation treatments themselves are painless. There are often uncomfortable side effects, however.

Radiation treatments can produce fatigue, particularly in the later stages of treatment. Treatments are often given five days a week for several weeks, sometimes twice per day. In these cases, the fatigue can last for a few weeks or longer after treatment ends.

Skin problems are fairly common, since the radiation is absorbed to some degree by the tissues covering the breast. Redness, itching and soreness can occur. There may be decreased sensation around the breast, under the arm and other areas nearby. Hair loss does not occur, unless radiation is applied directly to the head, which is rarely the case when treating breast cancer.

In more extreme cases, the immune system can be compromised, especially if radiation is applied to the lymph nodes in the armpit. Lymph nodes and the connecting vessels that run throughout the body, are a key component of the immune system and radiation can decrease their effectiveness.

Fortunately, side effects are usually short lived. Except in the most extreme cases, organs, lymph nodes and other body components are not destroyed or irreparably harmed by radiation treatment. Though function may be temporarily suppressed, the body generally bounces back.