Cancer of Unknown Primary: Radiation Therapy

What is radiation therapy?

Radiation therapy uses rays of energy to kill cancer cells. It can also make them grow slower. It can also harm normal cells near the tumor. This can cause side effects.

A doctor called a radiation oncologist does this type of treatment.

When might radiation therapy be used to treat cancer of unknown primary?

Radiation may be used to treat the symptoms of cancer of unknown primary (CUP). Sometimes radiation may also be used to cure the cancer if it hasn’t spread too far.

How is radiation therapy given for cancer of unknown primary?

Doctors give radiation for CUP in two ways – externally or internally. The type of radiation used depends on the location, size, and spread of the cancer.

External radiation 

External radiation is the most common radiation treatment for CUP. A large machine directs rays of energy to the area of cancer. This is a lot like getting an X-ray. The treatments don't hurt and they’re quick. You’ll have treatments once a day, 4 to 5 days a week, for several weeks in a row.

Before you start treatment, you’ll have imaging scans in the area of your cancer. This is done to measure the location of the tumor so the beams of radiation can be focused there. You’ll receive small marks on your skin to mark the treatment area. This makes sure that the radiation reaches the tumor, and not healthy parts of your body.

On the day of treatment, you’ll be 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’re in the right position. The therapist will leave the room while the machine sends radiation to your tumor. During this time, he or she can see you, hear you, and talk to you. You’ll need to stay very still. But you don’t have to hold your breath. The process will likely take less than an hour.

Internal radiation

Internal radiation isn’t used as often to treat CUP. For this type of radiation, you’ll have an implant of tiny pellets of radiation placed in or near the tumor. The radiation travels a short distance to kill the cells around the pellet.

What are common side effects of radiation therapy?

Radiation affects both normal and cancer cells. This means it can cause side effects. The side effects you have depend on what part of your body is treated. Ask your healthcare provider what side effects you should watch for. Common side effects include the following:

• Diarrhea

• Fatigue

• Nausea

• Skin irritation. Your skin may become dry, red, and blister like a sunburn.

In most cases, these side effects go away after treatment. Your healthcare provider may give you medicines to help ease side effects.

Long-term side effects of radiation may not show up for years after you finish treatment. These effects depend on the dose and location of the radiation. They also depend on how many times you had the treatment. Ask your healthcare provider what to expect.

Working with your healthcare provider

Talk with your healthcare team about what signs to look for and when you should call them. For instance, radiation can harm your skin and make you more likely to get an infection.

It may be helpful to keep a log of your side effects. Write down physical, mental, and emotional changes. A written list will make it easier for you to remember your questions when you go to your checkups. It will also make it easier for you to work with your healthcare team to manage your side effects.