Week 11

"Radiation therapy uses a special kind of high-energy beam to damage cancer cells. (Other types of energy beams include light and x-rays.) These high-energy beams, which are invisible to the human eye, damage a cell’s DNA, the material that cells use to divide. Over time, the radiation damages cells that are in the path of its beam — normal cells as well as cancer cells. But radiation affects cancer cells more than normal cells. Cancer cells are very busy growing and multiplying — 2 activities that can be slowed or stopped by radiation damage. And because cancer cells are less organized than healthy cells, it's harder for them to repair the damage done by radiation. So cancer cells are more easily destroyed by radiation, while healthy, normal cells are better able to repair themselves and survive the treatment.

Radiation is an important and often necessary form of anti-cancer therapy because it is able to reduce the risk of recurrence after surgery. Although it's quite possible that your surgeon removed all the cancer, breast cancer surgery cannot guarantee that every last cancer cell has been removed from your body. Individual cancer cells are too small to be felt or seen during surgery or detected by testing. Any cells that remain after surgery can grow and eventually form a new lump or show up as an abnormality on a test such as a mammogram. Research has shown that people who are treated with radiation after lumpectomy are more likely to live longer, and remain cancer-free longer, than those who don't get radiation. In one large study, women who didn't get radiation after lumpectomy were shown to have a 60% greater risk of the cancer coming back in the same breast. Other research has shown that even women with very small cancers (1 centimeter or smaller) benefit from radiation after lumpectomy.

There are two main types of radiation:

External Radiation

External radiation is the most common type of radiation, typically given after lumpectomy and sometimes, mastectomy. In this section, you can read about how external radiation is given.

Internal Radiation

Internal radiation is a less common method of giving radiation. It is being studied for use after lumpectomy. In this section, you can read about how radiation is delivered inside the breast."

http://www.breastcancer.org/treatment/radiation/types/