Intensity Modulation Radiation Therapy (IMRT)

What Is IMRT?

Intensity-modulated radiation therapy (IMRT) is a very precise therapy that uses small radiation beams to treat cancer and non-cancerous tumors. It delivers beams of different intensities to conform to the targeted tumor’s shape, limiting the exposure to the surrounding tissues and minimizing side effects.

IMRT is an advanced type of radiation therapy that uses computer-controlled technology to send precise doses of radiation to a tumor. It uses 3D computed tomography (CT) or magnetic resonance images (MRI) to help determine the intensity and pattern of the beams, which customizes the treatment to each tumor.

The process uses a medical linear accelerator (LINAC) to generate the photons (X-rays) needed to treat tumors in the body and brain.

How Does IMRT Work?

Radiation kills cancer cells by damaging their DNA so they can’t reproduce. As the cancer cells die, the tumor shrinks.

IMRT points multiple beams of radiation at a tumor from outside the body. The separate beams can be adjusted to deliver different levels of intensity to different parts of the tumor, depending on its size, shape, and location. This allows doctors to deliver a precise amount of radiation to each part of the tumor while protecting the non-cancerous tissue surrounding the tumor as much as possible.

IMRT can treat many cancers, including:

• Bone
• Brain, head, and neck (malignant and benign tumors)
• Breast
• Esophageal
• Eye
• Liver
• Lung
• Lymphoma
• Pancreatic
• Prostate
• Rectal and anal
• Spine
• Stomach

IMRT Procedure

Your treatment will be managed by a specially trained team that may include a radiation oncologist, medical physicist, dosimetrist, radiation therapist, and radiation therapy nurse.

A week or two before your procedure, you’ll have a simulation appointment to prepare for the process. You’ll have a CT scan to create a 3D map of your tumor. Based on that 3D map, your doctor will put marks or gold seeds on your skin to help aim the radiation at the exact location every treatment.

You will have to be in the same position for each procedure. You may have a special mask or other devices fitted to help position and protect you during the procedure.

You may be given instructions to prep your bowel or bladder the night before the procedure or not to eat or drink after midnight.

The day of your procedure:

1. You may be given medication for anxiety if needed.
2. Your radiation therapist will help position you on the procedure table. If you had a special mask or equipment made to protect you or help you lie still, you’ll use those during every treatment.
3. While the radiation is being delivered, you’ll be alone in the treatment room, but you’ll be able to talk to your radiation therapist through an intercom.
4. The IMRT machine will be used to deliver the radiation beams to the tumor. The machine is as large as a small car, and it moves around your body during treatment. You won’t feel the radiation, but you will hear and smell the machine.
5. You may need to be repositioned throughout the procedure. You’ll be in the treatment room for 10 to 60 minutes, but you’ll only get the radiation for a few minutes.
6. After treatment, you can go home and do your normal activities. You will not need to stay away from other people.

Self-Care During Treatment

Treatment takes time. You may be scheduled for IMRT 5 days per week for up to 8 weeks. The number of treatments you need depends on your cancer and treatment plan.

It’s essential to take care of yourself during treatment to keep your strength up and to reduce any side effects if you can. In general, you should:

• Eat a healthy diet.
• Rest often – your body uses a lot of energy during treatment.
• Talk to your care team before taking any new medications, vitamins, or supplements.
• Take special care of your skin, which can become irritated by treatment:
  • Wear soft, loose clothing.
  • Don’t rub or scratch the treatment area.
  • Avoid hot and cold extremes on the treatment area. Don’t use ice packs or a heating pad. Only take lukewarm showers or baths.
  • Protect the treatment area from the sun with a hat or clothing.
  • Don’t shave the area or use soap, lotion, or deodorant on the treatment area unless your care team says it’s ok.

Side Effects

Side effects depend on the treatment location, the dose of radiation, and your overall health. If you have side effects, talk to your care team. They can give you advice about how to treat your side effects and decrease your chances of having them next time.
Early side effects may include:
Bladder and urinary changes
Diarrhea
Difficulty swallowing
Eating and digestion problems
Erectile dysfunction (ED)
Fatigue
Hair loss at the treatment area
Headaches
Nausea and vomiting
Skin sensitivity, redness, or swelling at the site of the radiation
Soreness at the treatment site

It’s possible to have side effects months or years after treatment. It’s rare, but when late symptoms do occur, they vary by treatment site and can include:

• Changes in the:
  • Brain
  • Bowel
  • Colon and rectum
  • Kidney
  • Joints
  • Lung
  • Mouth
  • Spinal cord
• Infertility
• Lymphedema
• Secondary cancer

Michael Selva, MD