Radiation therapy for salivary gland cancer

Radiation therapy uses high-energy x-rays or particles to destroy cancer cells or slow their rate of growth.

Radiation therapy may be used:

• As the main treatment (alone or with chemotherapy) in some cases of salivary gland cancer that cannot be removed by surgery because of the size or location of the tumor or if a person is in poor health
• After surgery (alone or with chemotherapy) as an adjuvant (additional) treatment to try to kill any cancer cells that may have been left behind (but were too small to be seen) if the tumor is thought to have a high chance of recurring (coming back)
• In people with advanced salivary gland cancer to help with symptoms such as pain, bleeding, or trouble swallowing

External beam radiation therapy, which focuses radiation from outside the body on the cancer, is the type of radiation therapy used most often to treat salivary gland cancer.

The treatment is much like getting an x-ray, but the radiation is more intense. The procedure itself is painless. Before your treatments start, the radiation team will take careful measurements to determine the correct angles for aiming the radiation beams and the proper dose of radiation. This may take a couple of hours or more on the first visit. After this, each daily treatment lasts only a few minutes, but the setup time -- the time to get you into place for treatment -- usually takes a bit longer. Most often, radiation treatments are given 5 days a week for 6 or 7 weeks.

In recent years, doctors have found that newer forms of radiation therapy may be more effective than the standard treatment. One approach is to give radiation twice a day over a shorter total length of time. This is known as accelerated hyperfractionated radiation therapy.

Doctors can now use 3-dimensional images (taken by CT or MRI scans) and computers to figure out how best to aim radiation at the cancer while limiting the radiation to normal tissues. This seems to lower side effects. Three-dimensional conformal radiation therapy (3D-CRT) and intensity-modulated radiation therapy (IMRT) are examples of this highly-focused approach to treatment.

Another approach is to use a special type of radiation known as fast neutron beam radiation. Instead of using x-rays, neutron radiation therapy uses a beam of high-energy neutrons. Neutrons are electrically neutral particles that can be found in many atoms. Some studies have suggested that this type of radiation may be more effective, but it may also lead to more side effects. Neutron therapy machines are available in only a handful of cancer centers in the United States at this time.

Possible side effects

External beam radiation may cause sunburn-like skin changes, nausea, vomiting, and fatigue. Often these go away after treatment.

Radiation therapy of the salivary glands can cause specific problems, because several important structures in the head and neck may also get some radiation during treatment. The most common side effect from radiation to the salivary glands is reduced production of saliva, which can lead to a dry mouth (see below). Radiation can also cause a temporary sore throat, sores in the mouth and throat, hoarseness, trouble swallowing, temporary partial or complete loss of taste, bone pain, and bone damage. Radiation can also make tooth problems worse. Most doctors advise that you have your teeth checked by a dentist prior to radiation therapy to the head or neck area. In some cases, the dentist may even recommend removing some teeth before treatment to lessen the chance you will have problems later.

For most major salivary gland cancers, radiation is only given to the side of the face and neck with the cancer, which reduces the risk of serious long-term side effects. But in rare instances, it may be necessary to treat both sides of your face and neck with radiation. This may damage other salivary glands, resulting in a permanently dry mouth. Dry mouth often causes problems with eating and swallowing and can lead to tooth decay.

Some of the damage to the salivary glands may be lessened if a drug called amifostine (Ethyol^®) is given before each radiation treatment. This drug can be hard to tolerate, so it is not appropriate for everyone.

Radiation therapy may also damage your thyroid gland. It can take months or even years before the thyroid stops putting out enough thyroid hormone. Tests of thyroid function will be done during follow up (after treatment is complete). Some patients later need to take pills to replace thyroid hormone.

It is important to discuss the possible side effects of radiation therapy with your doctor before starting treatment, and to make sure everything is being done to try to limit these side effects as much as possible. If you do have side effects, there are ways to relieve many of them, so it is important to discuss your symptoms with your cancer care team.

For more information on radiation therapy, see our document called Understanding Radiation Therapy: A Guide for Patients and Families.