Radiation Therapy for Salivary Gland Cancer

Studies have shown that people with squamous cell cancers of the head and neck who are treated at centers that treat a lot of head and neck cancers with radiation, tend to live longer. Even though salivary gland cancers are rarely squamous cell cancers, they are not common and the operations tend to be complicated. Given this, it’s important to go to a cancer center and radiation oncologist who have experience treating these cancers.

Radiation therapy uses high-energy x-rays or particles to destroy cancer cells or slow their growth. It can be used in many ways to treat salivary gland cancer:

Radiation therapy may be used:

• As the main treatment (alone or with chemotherapy) for some salivary gland cancers that can’t be removed by surgery because of the size or location of the tumor
• As the main treatment (alone or with chemotherapy) or if a person can’t have (or doesn’t want) surgery
• After surgery, also called adjuvant radiation, (alone or with chemotherapy) to try to kill any cancer cells that might have been left behind to help lower the chances of the cancer coming back
• To help with symptoms, such as pain, bleeding, or trouble swallowing, in people with advanced salivary gland cancer

Chemoradiation (radiation given at the same time as chemotherapy) often works better than radiation alone, but it also has more side effects.

Radiation to this part of your body can cause problems for your teeth and gums, so it's important to see a dentist before starting treatment. A dentist can make sure your mouth is healthy before treatment. They might recommend that certain bad teeth be removed before you start radiation because they can increase your chance of infection. During and after treatment, your dentist can help check for and treat any problems that may come up, such as infection or tooth and bone damage.

Quit smoking before salivary gland treatment

If you smoke, it is important to quit. Smoking during radiation treatment can cause more side effects and a poor response to radiation, which can raise your risk of the cancer coming back (recurrence). Smoking after treatment also increases the chance of getting a new cancer. Quitting smoking for good (before treatment starts, if you can) is the best way to improve your chances for successful treatment. It is never too late to quit. For help, see How To Quit Using Tobacco.

External beam radiation for salivary gland cancers

External beam radiation therapy (EBRT), is the type of radiation therapy used most often to treat salivary gland cancer. It focuses radiation from outside the body onto the cancer.

Before starting EBRT, a somewhat flexible but sturdy mesh head and neck mask might be made to hold your head, neck, and shoulders in the exact same position for each treatment. Some people might feel a bit confined while this mask is on and might need to ask for medicine to help them relax during the treatment. Sometimes, the mask can be adjusted so that it is not too constricting. Discuss your options with your radiation oncologist. You might also be fitted for a bite block that you hold in your mouth during treatment.

Getting radiation treatment is much like getting an x-ray, but the radiation dose is stronger and aimed more precisely at the cancer. The procedure itself is painless and each treatment lasts only a few minutes. The setup time – getting you into place for treatment – often takes longer.

Types of external beam radiation therapy (EBRT)

There are more advanced EBRT techniques that help doctors focus and aim the radiation more precisely.

Three-dimensional conformal radiation therapy (3D-CRT) uses special computers to precisely map the location of the tumor. Several radiation beams are then shaped and aimed at the tumor from different directions, which makes it less likely to damage the normal tissues it passes through. The beams come together at the tumor to give a higher dose of radiation there.

Intensity modulated radiation therapy (IMRT) is an advanced form of 3D-CRT. It uses a computer-driven machine that moves around the patient as it delivers radiation. Along with shaping the beams and aiming them at the tumor from several angles, the intensity (strength) of the beams can be adjusted to limit the dose reaching the most sensitive nearby normal tissues. This may let the doctor give a higher dose to the tumor.

Proton beam radiation therapy focuses beams of protons instead of x-rays on the cancer. Unlike x-rays, which go through the patient and expose tissues to radiation both before and after they hit the tumor, protons only travel a certain distance, so the tissues behind the tumor are exposed to very little radiation. Even the tissues in front of the tumor see less radiation than the tumor itself. This means that proton beam radiation can deliver radiation to the cancer while doing less damage to nearby normal tissues. Because there are so many critical structures close by, proton beam radiation can be used to treat certain salivary gland tumors. Proton therapy can be a safe option in certain cases when using x-rays is not.

Proton therapy is not widely available in the United States. Proton therapy might also not be covered by all insurance companies at this time.

Fast neutron beam radiation uses a beam of high-energy neutrons instead of using x-rays. Neutrons are neutral particles in atoms. Some studies have suggested that this type of radiation may be more effective, but it may also lead to more side effects. There is only one neutron therapy center in the United States at this time.

Treatment schedules for external beam radiation therapy (EBRT)

Standard EBRT for salivary gland cancers is usually given in daily fractions (doses) 5 days a week for about 6 to 7 weeks. But sometimes other schedules might be used:

• Hyperfractionation radiation is a slightly lower radiation dose given more than once a day (for example, twice a day for 7 weeks). 
• Accelerated fractionation radiation is the standard dose of radiation given each day but over a shorter time (5 to 6 weeks) instead of the usual 7 weeks (for example, radiation is given 6 days a week over 5 weeks instead of the standard 5 days a week for 7 weeks). 
• Hypofractionation radiation is a slightly higher radiation dose given each day to lessen the number of treatments (for example, a higher radiation dose is given each day for 6 weeks, not the standard 7 weeks).

Possible side effects of radiation therapy for salivary gland cancer

If you are going to get radiation therapy, it’s important to ask your doctor about the possible side effects so you know what to expect.

Short-term side effects of radiation therapy

Radiation to the cheek, mouth, and throat area can cause several short-term side effects depending on where the radiation is aimed and can include:

• Skin changes like a sunburn or suntan in the treated area
• Loss of taste
• Redness, soreness, or even pain in the mouth and throat
• Dry mouth
• Trouble swallowing
• Feeling tired
• Open sores in the mouth and throat
• Hoarseness

Often these go away over time after treatment ends.

Long-lasting or permanent side effects of radiation therapy

Poor nutrition and trouble swallowing: Many people treated with radiation to the salivary gland area have painful sores in the mouth and throat that can make it very hard to eat and drink. This can lead to weight loss and poor nutrition. The sores heal with time after the radiation ends, but some people continue to have problems swallowing long after treatment ends because of the tightening of the muscles caused by radiation. Ask your speech pathologist about swallowing exercises you can do to help keep those muscles working and increase your chance of eating normally after treatment. Liquid feeding through a tube placed into the stomach might be needed. (See Surgery for Salivary Gland Cancer for more on tube feedings.)

Dry mouth: Damage to the salivary (spit) glands from radiation can cause a dry mouth that doesn't get better with time. For most major salivary gland cancers, radiation is only given to the side of the face and neck with the cancer. This reduces the risk of serious long-term side effects, but in rare instances, both sides of your face and neck might need to be treated with radiation. This may damage other salivary glands, resulting in permanently dry mouth. This can lead to discomfort and problems eating and swallowing, as well as damage to the jaw bone.

The lack of saliva can also lead to tooth decay (cavities). People treated with radiation to the mouth or neck need to practice careful oral hygiene to help prevent this problem and see their dentist regularly. Fluoride treatments may also help.

Damage to the jawbone: This problem, known as osteoradionecrosis of the jaw, can be a serious side effect of radiation treatment. This is more common after tooth infection, extraction, or trauma, and it can be hard to treat. The main symptom is pain in the jaw. In some cases, the bone actually breaks. Sometimes the fractured bone heals by itself, but often the damaged bone will have to be repaired with surgery.

To help prevent this problem, people getting radiation to the mouth or throat area need to see a dentist to have any problems with their teeth treated before radiation is started. In some cases, teeth may need to be removed.

Lockjaw: Lockjaw, also knows as trismus, is a condition in which the mouth cannot open fully. This can be a serious side effect of radiation treatment. It happens because of scarring or damage to the muscles, joints, and tissue that help the jaw work. This can make it hard for people to chew their food well, speak properly, and can increase the chance of cavities. Not everyone who gets radiation for salivary gland cancer will have this side effect, but spotting the problem early can help people start treatment sooner and lower the chances that it will cause major troubles.

Hearing loss: The nerves or organs that help you hear can be damaged by radiation. You might be asked to see an audiologist (a person who specializes in hearing) to test your hearing before and after treatment to watch for any signs of hearing loss.

Thyroid problems: Radiation might damage your thyroid gland. Your doctor will do blood tests regularly to see how well your thyroid is working. Some people might need to take pills to replace thyroid hormone at some point if the thyroid gland is not working well.

Lymphedema: Some people treated with radiation therapy might be at risk of developing lymphedema in the head and neck areas that were treated. These areas can become swollen and firm. This can be worse if the person also had surgery. Sometimes, medicines, physical therapy, or massage therapy might be helpful.

Damage to the carotid artery: Radiation to the neck area might increase a person’s risk of stroke many years after treatment. This might be because of health problems that were already present before radiation such as narrowing of the artery or an increase in plaques both of which can decrease blood flow. People who smoke are also damaging their arteries. Because of this some doctors might order regular ultrasounds for you after treatment, to keep an eye on the arteries.

It’s 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 lessen many of them, so be sure to discuss any problems with your cancer care team.