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Cancer of Unknown Primary: Radiation Therapy 

What is radiation therapy?

Radiation therapy uses rays of energy or particles to kill cancer cells or 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 alone or with other treatments 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 2 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 type used for CUP. A large machine directs rays of energy to the tumor. This is like getting an X-ray. The treatments don't hurt and they’re quick. You’ll likely get treatments once a day, 5 days a week, for several weeks in a row.

Before you start treatment, you’ll have imaging scans. This is to measure the exact location of the tumor so the beams of radiation can be focused there. Small marks or tattoos might be put on your skin to mark the treatment area. This makes sure that the radiation is given to the right place each time and that it's focused on the tumor, and not healthy parts of your body.

On the day of treatment, you’ll be put into position. Casts or molds might be made to put you in the right position and keep you from moving. 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, you can talk to and hear the therapist through an intercom. You’ll need to stay very still. But you don’t have to hold your breath. The whole process will likely take an hour or so, but the treatment only takes few minutes.

Internal radiation

Internal radiation isn’t used as often to treat CUP. For this type of radiation, an implant of tiny pellets of radiation are put 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 the part of your body that's treated. Ask your healthcare provider what side effects you should watch for. Common side effects include:

  • Diarrhea

  • Fatigue

  • Nausea

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

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

Long-term side effects of radiation may not show up until 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 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. Know how to get help after office hours and on weekends and holidays.

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 check-ups. It will also make it easier for you to work with your healthcare team to manage your side effects.

Online Medical Reviewer: Kimberly Stump-Sutliff RN MSN AOCNS
Online Medical Reviewer: Lu Cunningham
Online Medical Reviewer: Richard LoCicero MD
Date Last Reviewed: 3/1/2019
© 2021 The StayWell Company, LLC. All rights reserved. This information is not intended as a substitute for professional medical care. Always follow your healthcare provider's instructions.
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