Thyroid Cancer: External Radiation Therapy
What is external radiation therapy?
In radiation therapy, strong, high-energy rays kill cancer cells or slow their growth.
In external radiation therapy, the radiation is aimed at the cancer from a source
outside the body.
External radiation is a local therapy. This means it affects the cancer cells only
in treated areas. This type of radiation may be given alone, with chemotherapy, or
with hormone therapy. It is sometimes used before surgery to shrink tumors. It may
be used after surgery to kill cancer cells left behind. External radiation may also
be used to treat cancers that can’t be removed with surgery.
When is external radiation therapy used to treat thyroid cancer?
External beam radiation therapy is not a common treatment for thyroid cancer.
It may be used to treat thyroid cancers that don’t take up iodine, such as anaplastic
or medullary cancer. It is also helpful when radioactive iodine (RAI) was tried, but
the cancer cells didn’t absorb the iodine well.
It can be used to treat areas where the cancer has spread, such as the bones or the
What to expect during external radiation therapy
Radiation treatment is a lot like getting an X-ray. The radiation comes from a large
machine. The machine doesn't touch you during the treatment. The treatments don't
hurt and they are quick.
This therapy is often given once a day, 5 days a week, for about 5 to 6 weeks. The
actual treatment time you spend receiving the radiation is often just a few minutes.
But it takes more time to get you into place and set up the procedure.
Before you start treatment, imaging scans will be done in the area of your cancer.
This is done to measure the exact location of the tumor so the beams of radiation
can be focused there. Small marks may be put on your skin to mark the treatment area.
This ensures that the radiation reaches only the tumor, and not healthy parts of your
body. On the day of treatment, you are carefully put into the right position. You
may see lights from the machine lined up with the marks on your skin. These help the
therapist know you are in the right position. The therapist will leave the room while
the machine sends radiation to your tumor. During this time, they can see you, hear
you, and talk to you. When the machine sends radiation to your tumor, you will need
to be very still, but you don't have to hold your breath. The treatment itself is
a lot like getting an X-ray and is very quick. The whole process will likely take
less than an hour.
Side effects of external radiation therapy
Radiation therapy affects normal cells as well as cancer cells. Talk with your healthcare
provider about what you might feel like during and after radiation therapy. Side effects
often get worse as treatment goes on. But remember, these side effects can be treated.
Common side effects of external radiation for thyroid cancer can include:
Severe tiredness (fatigue)
Loss of appetite
Low blood counts
Skin that feels and looks like it's sunburned (dry, red, and blistered) in the treated
Most of these side effects will get better or go away over time after you finish treatment.
Your healthcare provider will talk with you about how to manage these and other possible
long-term side effects. This includes injury to the esophagus, which might require
a feeding tube.
Working with your healthcare team
Ask your healthcare provider about what symptoms to watch out for and when you should
call your healthcare team. For instance, your healthcare provider may want you to
call if you have signs of infection, such as fever, or pain that gets worse. Make
sure you know what number to call with questions. Is there a different number for
evenings and weekends?
It may be helpful to keep a diary of your side effects. Write down any physical, thinking,
and emotional changes. A written list will make it easier for you to remember your
questions when you go to your appointments. It will also make it easier for you to
work with your healthcare team to make a plan to manage your side effects.