How Radiation Works to Fight Breast Cancer

Woman receiving Radiation Therapy Treatments for Cancer
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If you're using a flashlight in a dark room, you can see the light as a beam, which you can aim at objects. The beam from a flashlight starts out the same size as the lens, and widens until it touches a surface, such as the floor, or the wall. If you aim the light through a window, it will pass right through and illuminate whatever is on the outside.

Radiation therapy behaves in a similar way to the flashlight beam, but it possesses much more energy and is not visible to our eyes. Like the light of the flashlight passing through a window, the beam of radiation will pass through breast tissue as it hits your cells. During treatment, high-energy beams of radiation will be carefully aimed at the area of the breast from which the cancer was removed. These beams of radiation will affect cancer cells and healthy cells.

Cancer cells grow and divide much more quickly than healthy cells, and their internal functions are not well organized. This makes them more susceptible to damage from radiation treatment, and therefore less able to repair themselves and recover. That is the reason that they are destroyed by the radiation.

Healthy cells grow and divide at a normal speed, and they are well organized and robust. When healthy cells receive radiation, alongside cancer cells, the healthy cells will get damaged, but most are able to recover and repair themselves. They can survive the radiation treatment.

Two Methods of Radiation

External Radiation


The most commonly given treatment is external radiation, given as whole breast radiation (WBI) or partial breast radiation (EB-PBI). It is given daily for 5 to 7 weeks, and should be painless. Your doctor will explain how much radiation is needed, and what you can expect to experience. Be sure to ask about how to prevent, or deal with these possible side effects:

  • skin changes during and after treatment
  • discomfort near recent surgical scars
  • fatigue from radiation
  • swelling or stiffening of breast tissue
  • pain related to radiation
  • scar tissue in the lungs or heart

Internal Radiation (Brachytherapy)

This kind of radiation treatment is less common, but it can be used at the end of a course of radiation as a boost. Small pieces of radioactive material, which are sometimes called seeds, will be placed inside your breast, where the tumor used to be. The radiation from the seeds will affect the tissue around them, which includes any cancer cells. When the booster treatment is completed, the seeds will be removed.

How to Know What Type Is Right For you

Talking with your oncologist will help you decide which method will give you the most benefit, and will lower your risk of recurrence. A radiation oncologist will be able to guide you through the decision and treatment process, as well as explain the results of any x-rays that may be needed.

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