Radiation therapy

What is it?

Radiation therapy is a form of cancer treatment that uses an intense form of energy, called ionizing radiation, to damage or destroy cancer cells. Ionizing radiation harms cancer cells' genetic material. This kills the cells or interferes with their ability to grow and multiply. Normal cells near a tumor can be damaged as well. However, normal cells can repair any damaged genetic material, so they often recover and survive. Cancer cells generally can't make such repairs, so they die.

Radiation therapy can be given externally in the form of x-ray beams, gamma rays, or beams of subatomic particles such as protons. Treatment with external radiation is usually painless and takes five to 15 minutes per session. The number of treatments varies for each person. In some cases, therapy may take place almost every day for several weeks.

Radiation also can be delivered internally. Radioactive substances are either placed inside a body cavity or implanted inside the tumor itself.

Some doctors use these techniques to increase the effectiveness of radiation therapy:

• Conformal beam techniques — Radiation is delivered from many beams at the same time. This allows the radiation to be concentrated on the tumor with less damage to nearby normal tissues.
• Intraoperative radiation therapy — Radiation is delivered to a tumor during surgery.
• Radiosensitizers — These drugs increase radiation's damaging effect on cancer cells.
• Radioimmunotherapy — Radioactive substances are attached to antibodies, defensive chemicals made by the body's immune system. These antibodies target cancer cells and deliver damaging radioactivity only to them. Because the antibodies do not attack healthy cells, the possibility of radiation damage outside the tumor drops.

What it's used for

Radiation therapy is used to treat many types of cancer, including cancer of the lung, breast, prostate, testicles, and brain.

When a tumor is going to be removed surgically, radiation can shrink it. This reduces the amount of normal tissue that needs to be removed near the tumor. When cancer has spread, radiation therapy can be combined with chemotherapy or surgery to improve the chance of a cure. It can also be used to treat tumors blocking organs or tissues, such as a kidney or the spinal cord.

Radiation therapy can also reduce pain and other symptoms that may occur when cancer spreads. It may lessen the chances of a fracture if cancer has spread to the bones.

Preparation

Before you begin radiation therapy, you should take these steps:

• Visit your dentist and have any major dental work done if your head or neck will receive radiation. Radiation therapy can affect your teeth.
• Discuss family planning issues with your doctor, including the option of sperm banking, if you want to have children. Radiation to certain parts of the body can increase your risk of infertility or sterility. If you are a woman and you might be pregnant, tell your doctor.
• Ask your doctor if any medications you take could cause problems during radiation therapy.
• Consider reducing your work schedule or taking vacation time during treatments, if you work. Radiation therapy can make you tired.

You also might want to arrange for a friend or family member to drive you to therapy.

Because radiation can irritate skin in the treatment area, wear loose clothing that doesn't rub or bind.

How it's done

External beam radiation therapy

Before external radiation therapy begins, a radiation oncologist will plan your treatments. He or she will determine the dose of radiation, how it will be delivered, and the number of treatment sessions.

You will participate in a simulation session to help the radiation oncologist plan the treatment. He or she might mark your skin with tiny permanent or semi-permanent tattoos. This helps ensure that the radiation hits the same spot every time.

Alternatively, he or she may implant tiny gold seeds in your body. Called gold fiducials, they mark the edges of the area to be treated; they are viewed with imaging equipment at the start of each therapy session.

These techniques make focusing the radiation beam as accurate as possible from one treatment session to the next. It also lowers the risk that radiation will strike and damage normal tissue. For some cancers in the pelvis, having a full bladder helps focus the radiation beam.

Depending on the body area to be treated, you might need to remove your clothing and put on a hospital gown. In the radiation therapy room, you will lie on a table or sit in a special chair.

The therapist will check the marks on your skin (or the location of the fiducials) to find the exact treatment area. Special blocks or shields will protect other parts of your body. You need to be in the same position and remain still during every treatment so that the radiation hits its target. That's why a mold may be made of part of your body; you will be placed in the mold for treatment.

After you are positioned, the radiation oncologist will go to a control room nearby. From there, he or she will operate the treatment machine while watching you on a monitor or through a window. You might hear the machine make buzzing noises, and it might rotate around you.

Treatments typically are painless and brief, lasting one to five minutes. Your total time in the treatment room will be about five to 15 minutes. Usually, treatments will be given every weekday for several weeks. The weekend break gives normal cells affected by radiation some time to recover.

The type of radiation you receive and how it's delivered can vary from one center to another. Nearly all centers use some type of three-dimensional planning, called three-dimensional conformal radiation therapy, or 3D-CRT. Radiation oncologists and physicists determine the angles at which the radiation beams should enter the tissue. In this way, the radiation field conforms to the shape of the area to be treated.

Intensity-modulated radiation therapy (IMRT) is a form of 3D-CRT. It allows doctors to change the intensity of the radiation within each of the radiation beams. This increases the amount of radiation delivered to the tumor. It also helps spare healthy tissue.

Proton beam therapy uses beams of protons instead of x-rays. Proton therapy may be recommended for treating certain parts of the body, such as the eyes, face, skull, and spine.

Another device, called CyberKnife, accurately delivers very high doses of radiation. This shortens the total time needed for therapy. For example, traditional radiation therapy may last six to eight weeks. With CyberKnife, treatment may last just a few days.

Internal radiation therapy

If you are having internal radiation therapy, your treatment will be different. One type of internal radiation therapy is brachytherapy. (It's also called interstitial radiation therapy or "seed" therapy.) If you have this procedure, you will be given anesthesia. Radioactive seeds will be implanted directly into the tumor or a nearby area. The seeds will remain in your body permanently or be removed after a period of time, depending on the cancer.

Another type, called intracavitary therapy, involves placing radioactive material directly inside a body cavity, such as the uterus, vagina, or rectum. The radioactive material will be removed after a period of time.

Follow-up

Doctors use physical exams, imaging tests, x-rays, and blood tests to evaluate the progress of radiation therapy. The type of follow-up you need will vary depending on the type of cancer you have and how far it has spread.

Risks

The side effects of radiation therapy vary depending on the body area being treated. These include:

• fatigue
• skin irritation
• hair loss (permanent or temporary)
• change in skin color in the treatment area (temporary)
• loss of appetite
• nausea and vomiting
• constipation
• cramps and diarrhea
• infertility or sterility
• vaginal dryness or narrowing
• impotence.

Radiation therapy also can increase the risk of developing a second cancer. This is especially true in people who received radiation as children. Common second cancers include thyroid cancer and leukemia.

When to call a professional

Call your doctor if:

• your skin in the treatment area becomes painful, bright red, or moist and weepy
• you have severe or persistent nausea, vomiting or diarrhea.

He or she can prescribe medication to treat these side effects.

If your throat or mouth is sore, ask about a medicated mouthwash to make eating and swallowing more comfortable.

Additional info

National Cancer Institute (NCI)
https://www.cancer.gov

American Cancer Society (ACS)
https://www.cancer.org/