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External beam radiation (also called External Radiation) is radiation delivered by a machine (a linear accelerator) directly to a tumor site under the supervision of a cancer doctor who is known as a Radiation Oncologist. 

When planning your treatment, the radiation oncologist considers a variety of factors which determine the type of radiation therapy, the dose to be used and the treatment schedule. The factors used include:
  • The characteristics of your cancer 
  • The sensitivity of the tumor to radiation
  • The vulnerability of nearby normal tissues. 

The radiation dose is normally the same for each session. However, there may be variations.

While waiting for treatment to begin, there are steps to take. For instance, see your dentist. Talk with your doctor about the drugs, vitamins etc you take in case he or she wants you to stop taking them temporarily.

Before your first session, there will be a planning session. It is advisable to take a family member of friend with you to the meeting. It is also helpful to record the session.

Don't be surprised if the start of radiation treatment makes cancer feel real.

External bream radiation is given over a period of time which gives radiated skin time to heal between sessions.

There are do's and don'ts to be aware of during treatment. For example, don't apply powder to the radiated area before treatment. Speak with your radiologist if you have to miss a day or two. The efficiency of the  treatment depends on having as few delays as possible.

Other side effects such as skin irritation and fatigue during treatment are either controllable or there are techniques to lessen the effect. There may also be long term side effects. 

Keep in mind that treatment decisions may change as treatment goes along. A change does not mean that the original treatment was wrong. Medicine is a combination of science and art.

  • If needed, transportation is available to and from treatment.
  • If you are uncomfortable in a hospital gown, make your own or buy a substitute.

Women: Avoid getting pregnant during radiation treatment.

Men: If radiation is to the prostate or pelvic area, It is fairly common to experience erectile dysfunction during radiation treatment. Erectile dysfunction may continue for up to several years, or it may be permanent. There are techniques to overcome this situation.

NOTE: For questions to ask before agreeing to radiation, click here

Side Effects From External Radiation: During Treatment

While radiation therapy is safe, there are few possible short and long term side effects of EBRT. Side effects vary from patient to patient and according to the exact location of the radiation. Most side effects are due to the fact that the radiation beam affects normal tissues around the tumor area.

Normal daily activities can usually be continued during treatment. 

Common side effects include:

  • Fatigue (the most common symptom of radiation therapy)
    • Generally there is no fatigue during the first weeks of treatment.
    • Whether fatigue appears after that, and to what degree, depends on the individual.
    • If fatigue does appear, it generally plateaus around week 5.
    • Techniques are available for decreasing the effects of fatigue. 
    • Fatigue generally goes away within a week to a week and a half after end of treatment.
    • Fatigue does not generally keep people from working during treatment.
    • For tips on how to deal with fatigue, see the document in To Learn More.
  • Bladder irritability which shows up as a need to urinate more frequently than normally.  If this symptom shows up, it can continue for a while after end of treatment.
    • There is generally no need for a catheter (a tube through the penis to the bladder to ease urination).
    • Men who have severe urinary problems before starting EBRT are at risk for needing a catheter during EBRT.
  • Bowel irritation with may progress to diarrhea toward the end of treatment.
    • If diarrhea appears, it may continue for a week or two after the end of treatment.
    • Drink plenty of clear liquids to make up for the fluids being lost due to diarrhea.
    • For tips on how to deal with diarrhea, click here.
  • Erectile dysfunction.
    • Whether you experience erectile dysfunction after EBRT depends on:
      • Your potency level prior to the start of treatment. 
      • Your age
      • Other medical conditions which could effect erectile function such as diabetes, hypertension or cardio vascular disease.
    • If erectile dysfunction occurs, there is assistance available.See the Survivorship A to Z document about erectile dysfunction.
    • There are ways to be intimate other than by having sex. Plus there is plenty of stimulation you can get and receive that doesn't involve an erection. Speak with your doctor for more information or for a referral to an expert in the area.
    • If your medical condition is interfering wit h your sexual relations with your significant other, tell your significant other about your feelings and what you would like to change. Ask for your significant other's point of view. Listen to it rather than prepare your response. If the two of you can't work it out, speak with your doctor or seek counseling.
  • Temporary pain upon ejaculation and a permanent decrease in semen volume.
  • Incontinence (in the sense that urine leaks out of the penis unintentionally). For some men, incontinence happens when doing activities such as sitting. For some men it only happens when there is increased abdominal pressure – such as from laughing, coughing, sneezing or exercise.
    • EBRT rarely causes incontinence.
    • If a man is already incontinent before EBRT, incontinence tends to remain.
    • Sometimes, urinary frequency can feel like incontinence because the bladder sits on the prostate.  As noted above, this goes away over time when caused by EBRT.
    • There are tips for dealing with incontinence. See the document in “To Learn More.”
  • Your white blood cell counts may drop during radiation treatment. White blood cells fight infection and prevent bleeding. If blood tests show this problem, you may have to put treatments on hold for a week or two to allow your blood counts to come back up. 

What External Beam Radiation Is

External beam radiation comes from a machine.

There are many safeguards to protect you from unnecessary radiation to the parts of your body that do not need treatment.  All the machines are shielded so that the large amounts of radiation are given only to a specific area.

External radiation therapy is usually given on an outpatient basis in a hospital or clinic. Internal radiation usually requires hospitalization for a few days. 

Daily radiation doses are relatively small to prevent excessive skin burning.

Radiation treatments are spread out over several weeks to give the skin time to heal between doses. The result is less damage to the skin and other tissues while still providing the full dose. 

The External Radiation Team

External Beam Radiation Therapy is performed by a team which includes the following people:

Radiation oncologist: 

  •  An oncologist who specializes in radiation)
  • The radiation oncologist does the planning for the radiation treatment and manages you medically throughout the therapy. 
  • The radiation oncologist also oversees the quality of the therapy.

Radiation physicist:

  • Maintains the radiation equipment and related computers. 
  • Is involved with setting the treatment plan.

Radiation technologist: The person who administers the treatment plan.  The radiation therapist also brings you into the treatment room, sets you into correct position for the treatment, and turns the machine on and off. 

Radiation nurse: The person who schedules your appointments and answers your questions.

Steps To Take While Waiting For Treatment To Start

  • Schedule a dental check up. Oral infections can worsen the effects of radiation.
  • Find out if there are any medications, supplements, herbs or vitamins you take that should be discontinued during treatment. If there are, check with the doctor who prescribed them to let him or her know what is happening and find out if you should be doing something else during treatment.
  • Learn about the other side effects that frequently occur with radiation and how to eliminate or minimize them. Get prescriptions for medications that may minimize or help you cope with such side effects. Prescriptions don't cost anything until you have them filled. If you have the prescriptions, you can fill them without delay if the need arises. 
  • If you smoke, use the treatment as a trigger to stop. 
    • Stopping can help improve the body’s response to treatment, and lessen complications and side effects.
    • If you quit permanently, stopping can decrease the risk of recurrence and enhance survival. (To learn how to quit smoking, click here). 
  • If you use recreational drugs, let your doctor know. They may interfere with treatment.
  • If you want to have children in the future, ask if a treatment could affect your ability to have them. If so, consider banking your sperm before the treatment starts.
  • Consider taking a tour of the area where radiation will be administered and any other location where you will be spending time. This way you will know what to expect. You'll also get a better idea of what to bring with you to make yourself comfortable.
  • Speak with the radiologist about creams to purchase to reduce possible skin soreness. Test a small amount to be sure you don't have any adverse effects.
  • If you are uncomfortable in institutional hospital gowns, consider creating your own or purchasing one that will be more comfortable than the one supplied by the facility. You can find gowns online(for example, through offsite link) or create your own. For a pattern, see the document in To Learn More.
  • Think about how you are going to get to and from appointments. If needed, American Cancer Society can help arrange transportation with its group of volunteer drivers. Call 800.ACS.2345. The more notice you give the Society, the more likely it can find a volunteer to fill your needs. The Society can also point you to available public transportation in your area.
  • Ask your doctor about changes to start making in your diet to build your system with nutrients that the treatment may affect. The doctor may recommend you speak with a nutritionist/dietitian. Perhaps you should also be taking a multi-vitamin and/or supplements.
  • Stock up on your comfort foods, including some in your freezer that you can defrost as needed. When you freeze foods for this period, make the portions smaller than usual for those occasions when you don't feel like eating a lot.

Last, but not least, check your health insurance policy to determine how much, if at all, you will be out of pocket. If you don't have health insurance, start thinking about how to pay for the treatment. (See the documents in "To Learn More.")

What Happens During A Planning Session Before Your First Radiation Treatment

There will be a planning session at the radiation facility (generally the department of radiation oncology).

During the planning session:

  • You will meet the technicians and other personnel who will be involved in giving the treatment.
  • You will lie on a table. The radiation therapist will outline the treatment field and determine the settings of the machine.
  • The radiation therapist will position you in the position you will be in during the therapy. Molds may be created from plastic or plaster to help you remain in position during treatment.
  • The therapist will mark the skin around the treatment site with a pen to help assure the radiation is targeted to the correct area.
    • Do not wash off the mark unless it is made permanent. 
    • If the mark begins to fade, rather than make it darker yourself, tell the technician.
    • Ask if the mark can rub off on clothing and other material. If so, wear older undergarments that will cover the mark.
  • The therapist may permanently tattoo tiny dots around the field to be radiated. These dots are hardly noticeable because of their small size. They are made permanent in case you need additional radiation at a later date. Other radiologists will know where the previous radiation was given so the two don't overlap.

There will also likely be a mock session (known as a simulation) when you and the technician will run through a radiation treatment. A beam of laser light substitutes for radiation. The purpose of the mock session is to make sure everything is correct (some people refer to this as a "dress rehearsal.")  A simulation can take an hour or more.

Ask your radiologist about whether you can eat and drink prior to treatment. Generally you can, except for patients who take radiation to the abdomen.

What Happens During A Radiation Treatment

External radiation treatment is usually given at a set time on set days of the week. 

Before treatment begins

Generally, you change into a hospital gown. (You can bring one of your own design. If you are interested in making your own, for a pattern, see the document in "To Learn More."  Alternatively, gowns designed for purchase are also available. For instance, see offsite link

Then you will be taken into a treatment room which generallyu has thick concrete walls and lead-lined doors to protect people outside the treatment area from radiation.

You will be assisted onto the table or into the chair in which you will receive treatment. 

Blood may be drawn from time to time before the procedure starts to check your levels of white cells and platelets. They may become abnormally low during treatment. 

Radiation treatment is not invasive so there is no need for anesthesia.

It will take the technician a while to position you beneath the radiation unit. The tech may take a picture before treatment starts to be sure the field is aligned correctly. 

The technician will leave the room during treatment. You will be able to communicate via an intercom. The technician will also be able to visually observe you. 

Expect to be weighed at least once a week to see whether you are maintaining your normal weight. You may either lose or gain weight during treatment. 

The treatment

The actual treatment will generally only be a few minutes long. You don't have to hold your breadth. You will be able to breathe the whole time. (The whole appointment usually lasts fifteen minutes to a half hour).

Immediately after treatment

If you find you get queasy after treatment, it may because you have food in your stomach.

  • Next time, try fasting for several hours before and after each treatment. 
  • If nausea continues, let your radiation oncologist know. He or she can prescribe anti-nausea medication.

NOTE: If you experience nausea, consider not eating for several hours before and after each treatment. (There are other practical tips for dealing with nausea: see: To Learn More)

Activities during treatment:

  • Men generally can continue their regular schedule during radiation treatment, including exercise.
  • When it comes to exercise, check with your radiation oncologist. Even swimming is likely to be okay once skin markers are made permanent if you don’t let your skin become too dry.
  • Listen to your body and take good care of yourself.



What Happens After Radiation Treatment?

Expect to have follow-up visits with your radiation oncologist. The follow-up schedule depends on your particular cancer and health condition.

As a general matter, follow up starts with an appointment one month after the end of treatment (during which there will be a review of any lingering symptoms). For the next twoyears, there is likely to be a follow up appointment every six months. Follow up visits may be staggered between your radiation oncologist and other specialists such as a gastroenterologist or urologist. (If you do see more than one doctor, ask each of them to send a report of the visit to the other specialist, as well as to your primary care doctor). If things are going well, the interval between follow-up visits thereafter will likely be lengthened.

Side Effects From External Radiation: After Treatment

In general: As a general matter, side effects that appear during radiation treatment may continue for a short while after treatment ends, but then they will gradually disappear.

 If side effects continue longer than expected, contact your doctor. 

Erectile Dysfunction: If you experience erectile dysfunction during treatment, it may continue. It can go on for 2 – 5 years.  About one-half of men do complain of some erectile dysfunction after 5 or 6 years. There are treatments for erectile dysfunction. To learn more, see the document in To Learn More. 

Chemotherapy:  If you have chemotherapy after radiation treatment, some drugs used for chemotherapy may sensitize the skin to radiation. The skin that was exposed to the radiation beam may develop particularly severe inflammation, rashes, or sores. This is known as "radiation recall."  If it occurs, tell your doctor.

How To Choose A Radiation Oncologist

When looking for a cancer doctor who specialisizes in radiation treatment, consider the following:

  • Look for a doctor who is board certified in radiation oncology. Also look at the institution or institutions the doctor is affiliated with. The better the institution, the higher the standards which are applied to the professionals who are allowed to be affiliated with the institution.
  • Look at the treatment facility. 
    • The technology available to treat you can vary greatly from one facility to another. 
    • Travel time to the facility becomes important because treatment is likely to be daily over a period of weeks.
  • If you have health insurance, do the doctor and the facility accept it? If not, is there a less expensive doctor with the right qualifications who works in an acceptable facility that costs less?

Do's And Don'ts During Treatment


  • Arrive at each treatment session early.
  • Fast for several hours before and after each treatment if you find you get queasy after treatment.If nausea continues, let your radiation oncologist know. He or she can prescribe anti-nausea medication. (There are other practical tips for dealing with nausea: see: To Learn More).
  • Check with your radiation oncologist about exercise. 
  • Listen to your body and take care of yourself.


  • Put make up over the site markers.
  • Try to remove the treatment markers.
  • Skip a session if you can avoid it. Effectiveness depends on keeping to the planned schedule. If you have to miss a session, speak with your radiation oncologist to find out how to make it up.

To Learn More