Houston Methodist. Leading Medicine.
Houston Methodist. Leading Medicine

Methodist Cancer Center - Texas Medical Center

Radiation Therapy

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Radiation therapy uses X-rays and other high-energy rays to kill cancer cells in a specific area of the body

Types of Radiation Therapy
Preparing for Radiation Therapy
What to Expect From External Radiation Therapy
What to Expect From Internal Radiation Therapy
Side Effects of Radiation Therapy
Safety Measures for Internal Radiation Therapy
After Radiation Therapy

Types of Radiation Therapy
Radiation therapy can be given in two ways: from outside the body (external beam radiation) and from inside the body (internal radiation therapy).

External beam radiation is the most common approach to radiation therapy, in which radiation is delivered from a machine outside the body. Specific types of external beam radiation include three-dimensional conformal radiation therapy (3D-CRT), intensity modulated radiation therapy (IMRT), and stereotactic radiation therapy. Your doctor can explain the specific type of radiation recommended for your case.

Internal beam radiation involves placing radioactive material into the tumor itself or into the tissue surrounding it. One type of internal beam radiation is brachytherapy in which radioactive isotopes sealed in tiny pellets (“seeds”) are implanted using needles, catheters or some other type of carrier. As the radioactive material decays, it gives off radiation that kills nearby cancer cells. Internal radiation can also be delivered in a liquid form that you would receive orally or through an IV line.

Preparing for Radiation Therapy
During your initial visit, or consultation, your Radiation Oncologist will determine whether you are a candidate for radiation. This includes discussing course of therapy, side effects, and what to expect during your treatment.

If your doctor recommends external radiation therapy, you’ll go in for a simulation before the treatment begins. During this appointment, your radiation therapy team will:

  • Determine the exact location of the tumor (using an X-ray, a CT scan or an MRI), which will help them adjust the radiation beam to target the cancer as precisely as possible
  • Mark the tumor’s location on your skin with a small temporary tattoo, because it’s important that the radiation be delivered to the exact same spot every time
  • Select special blocks or shields to prevent the radiation from damaging healthy tissue

After the simulation, your team will design a specific plan outlining your course of radiation treatment.


What to Expect From External Radiation Therapy
External radiation therapy is painless, takes only a few minutes, and can often be done in a walk-in clinic. Because it takes time to set the machine up, your appointment may take a total of about 30 minutes. External beam radiation treatments are typically given 5 days a week for up to 10 weeks.

  • You’ll be asked to lie down on a treatment table under a radiation machine.
  • Your radiation therapist may put shields or blocks in place to protect certain areas of your body from the radiation.
  • Once you are in place and the machine is ready, your therapist will go to a nearby room to work the controls, and you’ll be able to communicate over an intercom.
  • While the machine is working, you’ll be asked to stay still (you can still breathe) and will hear a variety of clicking and whirring sounds.

The machine can be stopped at any time, so if you feel sick or begin to panic during the treatment, let the therapist know immediately.

What to Expect From Internal Radiation Therapy
Internal radiation treatments do not need to be repeated as often as external treatments, but they usually do require anesthesia and a brief hospital stay.

If you are undergoing brachytherapy:

  • You will first be put under either general or local anesthesia, depending on where the radiation is being placed.
  • Then the radioactive “seeds” are put in the body, usually through a catheter or other type of applicator.
  • Depending on your specific case, the radioactive material may stay in place for a few minutes, for several days or for the rest of your life.

If your doctor prescribes radiation therapy in liquid form, you’ll receive it orally (by drinking a fluid, swallowing a pill) or intravenously.

Safety Measures for Internal Radiation Therapy
Because internal radiation therapy places radioactive materials inside your body, your doctor will discuss some necessary safety measures to protect other people, which may include:

  • Being in a private hospital room
  • Limited contact with nurses and other hospital staff
  • Not allowing visitors to your room, or limiting visits to 30 minutes or less
  • Not having visits from pregnant women or children under 18

You may need to continue observing some safety measures after you return home, such as not coming into contact with pregnant women for a period of time. Your medical team will provide you with specific instructions when you leave the hospital.

Side Effects of Radiation Therapy
Depending on the type of radiation you receive and the area of the body involved, you may experience one or more of the following side effects:

  • Fatigue
  • Hair loss
  • Diarrhea
  • Mouth problems such as ulcers or a metallic taste
  • Nausea and vomiting
  • Sexual problems such as impotence
  • Skin changes such as redness, dryness or peeling
  • Sore throat
  • Problems urinating


After Radiation Therapy
After your radiation treatments end, you’ll need to see your radiation oncologist for follow-up visits to monitor your recovery and to check for side effects. As your body recovers from the treatments, you’ll need fewer follow-up appointments.


Learn more about cancer treatment:

For more information about radiation therapy at the Methodist Cancer Center or to make an appointment, call us at 713.441.4800.