External beam radiation therapy

How long does the treatment take?

For most people, treatments are given 5 days a week for 1 to 10 weeks. The number of treatments you need depends on the size and type of cancer, where the cancer is, how healthy you are, and what other treatments you are getting. Patients often get a break on weekends so their normal cells can recover.

What happens during each treatment visit?

External radiation therapy is like getting an x-ray. It’s painless and only takes a few minutes. But it takes time to get the machines set up, so it may take 15 to 30 minutes to get each treatment. It’s often given in a walk-in clinic, so you don’t have to be in the hospital.

You will lie flat on a treatment table, under the radiation machine. The radiation therapist may put special shields or blocks between the machine and other parts of your body. These protect your other body parts from the radiation. You will be asked to stay still during the treatment, but you don’t have to hold your breath.

Once you’re all set and the machine is ready, the therapist goes into a nearby room to run the machine and watch you. You and the therapist can talk over an intercom. While the machine is working, you’ll hear clicking and whirring. Sometimes you’ll hear something that sounds like a vacuum cleaner. That sound is the machine moving to aim the radiation. The radiation therapist controls this movement and checks to make sure the machine is working the way it should.

If you are worried about anything that happens while the machine is on, talk to the radiation therapist. If you start to feel sick or scared, let the therapist know right away. The machine can be stopped at any time.

The American Cancer Society medical and editorial content team
Our team is made up of doctors and master's-prepared nurses with deep knowledge of cancer care as well as journalists, editors, and translators with extensive experience in medical writing.

Last Medical Review: October 9, 2015 Last Revised: October 9, 2015

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