External Radiation Therapy

What is external radiation therapy?

Radiation therapy uses high-energy waves or particles to destroy cancer cells. New technology allows doctors to focus radiation on very small and specific areas, which kills unhealthy cells and leaves healthy cells unharmed.

During external radiation therapy, radiation comes from outside the body and is targeted at tumors or the areas around where tumors were located.

You may also receive external radiation therapy:

  • Before surgery, to shrink the size of tumors
  • After surgery, to kill any remaining cells
  • In place of surgery, if your tumor can't be removed

Types of external radiation therapy

New types of external radiation therapy allow you to receive high doses of radiation in fewer treatments. This cuts down your appointment times and, most importantly, kills cancer fast. Types of external radiation therapy include:

  • Stereotactic body radiation therapy (SBRT) uses precise, high-powered radiation that requires five treatments or fewer. Treatment sessions often take about a half an hour.
  • Stereotactic radiosurgery (SRS) uses one single, strong beam to kill cancer cells in the brain without harming healthy brain tissue.
  • Intensity modulated radiation therapy (IMRT) delivers radiation based on a 3D model of your tumor. This therapy changes how strong the radiation is, based on the shape of your tumor. For instance, areas that are only a few millimeters thick get weaker radiation than areas that are an inch thick. This way, the radiation doesn't hit your healthy cells around the tumor.

What makes external radiation therapy so accurate?

External radiation technology has become so advanced that machines that deliver radiation therapy even track how your tumor moves in real-time and adjusts radiation to match.

For instance, if you have a tumor in your lung, the machine will take into account the way the tumor moves when you breathe. As you breathe in and out, the radiation beams move so that they stay with the tumor and don't harm your healthy lung tissues. This is called respiratory gating technology.

External radiation therapy also uses image guidance to be sure to hit the tumor every time. Before your treatment, your doctors will take a computed tomography (CT) scan and precisely mark where the tumor is. Your scans are then loaded into the radiation machine. The machine senses where you are and won't even turn on radiation unless you line up exactly with your CT scan. This level of precision helps you keep as much healthy surrounding tissue as possible.

What to expect from an external radiation therapy treatment session

Depending on where your cancer is located, you may need to wear a gown during treatment. A nurse or technologist will help you lie in the correct spot for radiation. You may have special devices that help line you up in the right spot. Once you're in position, the technologist will leave the room so treatment can start.

During treatment, you'll lie very still, but breathe normally. The technologist will watch you from another room at all times. You won't feel any pain during the treatment. After treatment, the technologist will help you stand up or remove devices. You'll then change back into your clothes and go home.


Cancer Care

From diagnosis and throughout treatment, Main Line Health cancer specialists (oncologists) provide compassionate care for you and your loved ones through all stages of cancer treatment.