Radiation Therapy

This information will help you get ready for radiation therapy, including what to expect before, during, and after your treatment. You’ll also learn about side effects and how to care for yourself during your treatment.

We suggest you read through this resource at least once before you start radiation therapy, and then use it as a reference in the days leading up to your radiation treatments so you can do all you can to prepare. Bring it with you for your simulation appointment and all future appointments with your radiation oncologist so you and your healthcare team can refer to it.

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About Radiation Therapy

Radiation therapy uses high-energy rays to treat cancer. It works by damaging the cancer cells and making it hard for them to reproduce. Your body then is naturally able to get rid of these damaged cancer cells. Radiation therapy also affects normal cells. However, your normal cells are able to repair themselves in a way that cancer cells cannot.

During external beam radiation, a treatment machine will aim beams of radiation directly to the tumor. The beam passes through your body and destroys cancer cells in its path. You won’t see or feel the radiation.

Radiation therapy takes time to work. It takes days or weeks of treatment before cancer cells start to die, and they keep dying for weeks or months after radiation therapy ends.

You can have radiation before, during, or after surgery or chemotherapy.

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Your Role on Your Radiation Therapy Team

You’ll have a team of healthcare providers working together to provide the right care for you. You’re a part of that team, and your role includes:

  • Arriving on time for all your radiation therapy sessions.
  • Asking questions and talking about your concerns. We have included a list of possible questions at the end of this resource.
  • Letting someone on your radiation therapy team know when you have side effects.
  • Telling your doctor or nurse if you’re in pain.
  • Caring for yourself at home:
    • Quitting smoking, if you smoke. If you want to quit, call our Tobacco Treatment Program at 212-610-0507.
    • Following your radiation therapy team’s instructions to care of your skin.
    • Drinking liquids as instructed by your healthcare team.
    • Eating the foods suggested by your radiation therapy team.
    • Maintaining your weight.
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Before you begin your treatment, you’ll have a treatment planning procedure called a simulation. This is done to make sure that:

  • Your treatment site is mapped.
  • You get the right dose of radiation.
  • The amount of radiation that gets to your nearby tissues is as small as possible.

During your simulation, you’ll have x-rays and your skin will be marked with little tattoo dots. These marks identify the area that will be treated.

Your simulation will take at least an hour, but can be longer depending on the treatment your doctor has planned for you.

Getting ready for your simulation

You may need to follow additional instructions to get ready for simulation, depending on what area is being treated. Your nurse will review this with you.

  • Bowel preparation

  • Diet instructions

  • Medications

If you don’t need any special preparation, you can eat and drink as you normally would on the day of your simulation.

During your simulation, you’ll be lying in one position for a long time. If you think you’ll be uncomfortable lying still, you can take acetaminophen (Tylenol®) or your usual pain medication before your simulation. If you think you may get anxious during your procedure, speak with your doctor about whether medication may be helpful.

Wear comfortable clothes that are easy to take off because you may need to change into a hospital gown. Do not wear jewelry, powders, or lotions.

Remove devices from your skin

If you wear any of the following devices on your skin, the manufacturer recommends you remove it before your simulation or treatment:

  • Continuous glucose monitor (CGM)
  • Insulin pump

Talk with your radiation oncologist about whether you may need to remove your device before your simulation or treatment. Make sure you have an extra device with you to put on after your simulation or treatment.

If you’re not sure how to manage your glucose while your device is off, talk with the healthcare provider who manages your diabetes care before your appointment.

Day of your simulation

What to expect

A member of your radiation therapy team will check you in. You’ll be asked to state and spell your full name and birth date many times. This is for your safety. People with the same or similar names may be having care on the same day as you.

You’ll be greeted by your radiation therapist. He or she will take a photograph of your face. This picture will be used to identify you throughout your treatment.

Your therapist will then explain the simulation to you. If you haven’t already signed a consent form, your radiation oncologist will review everything with you, and ask for your signature.

During your simulation

For your simulation, you may need to get undressed and change into a gown. You should keep your shoes on. If you wear a head covering, such as a wig, turban, or cap, you may have to remove it. Your therapists will help you lie down on a table and make every effort to ensure your comfort and privacy.

Although the table will have a sheet on it, it’s hard and has no cushion. If you haven’t taken pain medication and think you may need it, tell your therapists before your simulation begins. Also, the room is usually cool. If you feel uncomfortable at any time, let your therapists know.

Throughout your simulation, you’ll feel the table move into different positions. The lights in the room will be turned on and off and you’ll see red laser lights on each wall. Your therapists use these laser lights as a guide when they position you on the table. Do not look directly into the red beam because it may damage your eyes.

Although your therapists will walk in and out of the room during your simulation, there will always be someone who can see and hear you. You’ll hear your therapists speaking to each other as they work, and they’ll explain to you what they are doing. Do not move once your simulation begins, because it may change your position. However, if you’re uncomfortable or need help, tell your therapists.

To help pass the time, your therapists can play music for you. You may bring a CD of your own from home, if you wish.


Depending on the area of your body that is being treated, you may lie on your stomach or on your back. Your arms may be raised above your head or at your sides.

We may need to make a mold of your body to help you stay in the same position. Making the mold takes about 15 minutes and will happen during your simulation. If you need a mold, you’ll lie in it during the simulation and every day of your treatment. This helps us make sure that you’re lying in the correct position.

X-ray images

While you’re lying in your position, you’ll get x-rays of the area to be treated. These may be done on an x-ray machine called a simulator or on a computed tomography (CT) scan machine (see Figure 1). These scans are used only to map your treatment. They aren’t used for diagnosis or to find tumors. If you need other imaging, your nurse will explain this to you.

Figure 1. Computed Tomography (CT) scan machine

Figure 1. Computed Tomography (CT) scan machine

It will take about 45 minutes to get your x-rays. During the scan, you’ll hear the machine turn on and off. Even if the noise seems loud, your therapists will be able to hear you if you speak with them.

Skin markings (tattoos)

Your therapists will draw on your skin in the area being treated with a felt marker. You may need permanent skin markings called tattoos. Your therapists will use a sterile needle and a drop of ink to make the tattoo. The sensation of getting one feels like a pinprick. The tattoo marks are no bigger than the head of a pin. The felt marking can be washed off after your simulation. The tattoos are permanent and won’t wash off. If you’re concerned about receiving tattoos as part of your radiation treatment, talk with your doctor.

After the tattoos are made, your therapists will take several photographs of you in your simulation position. The photographs and tattoo marks will be used to position you correctly on the table each day of your treatment.

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After Your Simulation

At the end of your simulation, we will give you an appointment for your set-up procedure. This is the final appointment before your treatment begins.

Scheduling your treatment

Radiation treatments may be given Monday through Friday. For some people, the treatment is given in just one day. For other people the treatment is given over a number of weeks. Your treatment will be given for about ______ days/weeks.

You must come in every day that you’re scheduled for your treatment. Treatment may not be as effective if you skip or miss appointments. If you need additional time due to unforeseen circumstances, your radiation oncologist will tell you. If you for some reason you can’t come in for treatment, you must call your radiation oncologist’s office to let your team know. If you need to change your schedule for any reason, speak with your radiation therapist.

Treatment planning

During the time between your simulation and start of treatment, your radiation oncologist will work with a team to plan your treatment. They’ll use your simulation x-rays and CT scan to plan the angles and shapes of your radiation beams. The details are carefully planned and checked. This takes between 5 days and 2 weeks.

Vitamins and dietary supplements

Many people ask about taking vitamins during treatment. You may take a daily multivitamin, if you wish. Do not take more than the recommended daily allowance of any vitamin. Do not take any other vitamins or any supplements without talking to your doctor. This includes both nutritional and herbal supplements.

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Set-up Procedure

Before your first treatment, you’ll be scheduled for a set-up procedure. This generally takes about 1 hour. If pain medication was helpful during simulation, you may want to take it before this procedure.

When you come for your set-up procedure, you’ll be shown to the dressing room and asked to change into a gown. Your therapists will bring you to the room where you’ll receive your treatment each day. They’ll position you on the treatment table. You’ll lie exactly as you were lying day of your simulation.

Special x-rays called beam films will be taken to make sure that your position and the area being treated are correct. The beam films will be repeated throughout your treatment. They aren’t used to see how your tumor responds to the treatment.

Depending on your treatment plan, you may start treatment on the same day as your set up procedure or 1 to 2 days later.

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During Your Treatment

After you check in at the reception desk, have a seat in the waiting room. When your radiation therapists are ready for you, they’ll tell you to change into a gown. You should keep your shoes on during the treatment.

Your radiation therapists will bring you into the treatment room and help you lie on the table (see Figure 2). You’ll be positioned exactly how you were lying during your set-up procedure.

Figure 2. Treatment

Figure 2. During your treatment

Once you’re positioned correctly, your therapists will leave the room, close the door, and begin your treatment. You won’t see or feel the radiation, but you may hear the machine as it moves around you and is turned on and off. You’ll be in the treatment room for 15 to 45 minutes, depending on your treatment plan. Most of this time will be spent putting you in the correct position. The actual treatment only takes a few minutes.

Although you’ll be alone during the treatment, your therapists will see you on a monitor and hear you through an intercom at all times. Your radiation therapist will make sure that you’re comfortable during the treatment. Breathe normally during the treatment, but do not move. However, if you’re uncomfortable or need help, speak to your therapists. They can turn off the machine and come in to see you at any time, if necessary.

Neither you, nor your clothes will become radioactive during or after treatment. It’s safe for you to be around other people.

Weekly visits during treatment

Your radiation oncologist and radiation nurse will see you each week to talk with you about any concerns, ask about any side effects you may be having, and answer your questions. This visit will be before or after your treatments each ________________. You should plan on being at your appointment about 1 extra hour on those days.

If you need to speak with your radiation oncologist or radiation nurse any time between your weekly visits, ask the support staff or your therapists to contact them when you come in for treatment.

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Side Effects

Some people develop side effects from radiation therapy. Which side effects and how severe they are depend on many factors, such as the area being treated, the dose of radiation, the number of treatments, and your overall health. The side effects may be worse if you’re also getting chemotherapy. Below are the most common side effects of radiation therapy. You may have all, some, or none of these.

Skin and hair reactions

During radiation therapy, your skin and hair in the area being treated may change. This is normal. After 2 to 3 weeks, your skin may become pink or tanned. It may even become bright red or very dark later on.

Your skin may feel dry and itchy, and may look flaky during treatment. Sometimes, the skin in sensitive areas may blister, open, and peel. If this happens, tell your doctor or nurse.

You may also notice a rash, especially in any area where you have had previous sun exposure. Although this may be a side effect of treatment, a rash could also be a sign of infection. If you develop a rash at any time during your treatment, tell your doctor or nurse.

Your nurse may apply special dressings or creams and teach you how to care for your skin. Your doctor may stop your treatment until your skin heals. This skin reaction sometimes becomes more severe during the week after treatment is done. If this happens, call your doctor or nurse. Your skin will gradually heal after your treatment is completed, but this often takes 3 to 4 weeks.

You may lose some or all of the hair in the area being treated. Your hair will usually grow back 3 to 6 months after your treatment is completed.

Below are guidelines to help you care for your skin during treatment. Follow these guidelines until your skin gets better. These guidelines refer only to the skin in the area being treated with radiation.

Keep your skin clean

  • Bathe or shower daily using warm water and a mild unscented soap, such as Neutrogena®, Dove®, baby soap, Basis®, or Cetaphil®. Rinse your skin well and pat it dry with a soft towel.
  • When washing, be gentle with your skin in the area being treated. Do not use a washcloth, a scrubbing cloth, or brush.
  • If you received tattoo marks before your treatment, they are permanent and won’t wash off. You may get other markings during treatment such as an outline of your treatment area with a purple felt-tipped marker. You can remove these markings with mineral oil when your therapists say it’s okay.
  • Do not use alcohol or alcohol pads on your skin in the area being treated.

Moisturize your skin often

  • Start using a moisturizer when you begin treatment. This can help to minimize any skin reaction. You can use over-the-counter moisturizers. When choosing a moisturizer pick one that does not have any fragrances or lanolin. There are a number of products that are good to use, and your nurse may suggest one of these to you. Use only one at a time unless your nurse tells you to use more.
  • If you’re using a moisturizer, apply it 2 times a day.

Avoid irritating your skin in the area being treated

  • Wear loose-fitting cotton clothing in the area being treated. Do not wear tight clothing that will rub against your skin.
  • Use only the moisturizers, creams, or lotions that are recommended by your doctor or nurse.
  • Don’t use makeup, perfumes, powders, or aftershave in the area being treated.
  • Don’t use deodorant if your skin is open, cracked, or irritated. You can use deodorant on intact skin in the area being treated. Stop using it if your skin becomes irritated.
  • If your skin is itchy, do not scratch it. Apply moisturizer. Ask your nurse for recommendations on how to relieve the itching.
  • Don’t shave in the area that is being treated. If you must shave, use only an electric razor. Stop if your skin becomes irritated.
  • Don’t put tape on your treated skin.
  • Don’t let your treated skin come into contact with extreme hot or cold temperatures. This includes hot tubs, water bottles, heating pads, and ice packs.
  • If you have no skin reactions during your treatment, you can swim in a chlorinated pool. However, be sure to rinse off the chlorine right after getting out of the pool.
  • Avoid tanning or burning your skin during treatment and for the rest of your life. If you’re going to be in the sun, use a PABA-free sunblock with an SPF of 30 or higher. Also, wear loose-fitting clothing that covers you as much as possible.


Fatigue is a feeling of feeling tired or weak, not wanting to do things, not being able to concentrate, or feeling slowed down. You may develop fatigue after 2 to 3 weeks of treatment, and it can range from mild to severe. Fatigue may last 6 weeks to 12 months after your treatment ends.

There are a lot of reasons why you may develop fatigue during treatment, including:

  • The effects of radiation on your body.
  • Traveling to and from treatment.
  • Not having enough restful sleep at night.
  • Not eating enough protein and calories.
  • Having pain or other symptoms.
  • Feeling anxious or depressed.
  • Certain medications.

You may find that your fatigue is worse at certain times of the day. Below are suggestions to help you manage your fatigue.

Ways to manage fatigue

  • If you’re working and are feeling well, continue to do so. However, working less may help increase your energy.
  • Plan your daily activities. Pick those things that are necessary and most important to you and do them when you have the most energy. For example, you may go to work but not do housework, or watch your children’s sports event but not go out to dinner.
  • Plan time to rest or take short naps (10 to 15 minutes) during the day, especially when you feel more tired. If you do nap, try to sleep for less than 1 hour at a time.
  • Try to sleep at least 8 hours every night. This may be more sleep than you needed before you started radiation therapy. You may also find it helpful to go to sleep earlier at night and get up later in the morning. One way to sleep better at night is to be active during the day. For example, if you’re able to exercise, you could go for a walk, do yoga, or ride a bike. Another way to sleep better at night is to relax before going to bed. You might read a book, work on a jigsaw puzzle, listen to music, or do calming hobbies.
  • Ask family and friends to help you with things like shopping, cooking, and cleaning. Check with your insurance company to see if they cover home care services.
  • Some people have more energy when they exercise. Ask your doctor if you can do light exercise, such as walking, stretching, or yoga.
  • Eat foods that are high in protein and calories. Ask your nurse for the resource Eating Well During Your Cancer Treatment.
  • Other symptoms, such as pain, nausea, diarrhea, difficulty sleeping, or feeling depressed or anxious, can increase your fatigue. Ask your doctor or nurse for help with any other symptoms you may have.

Other side effects

Some people may experience other side effects. Your radiation oncologist or nurse will discuss these with you.

Sexual and reproductive health

You can be sexually active during radiation treatment unless your radiation oncologist gives you other instructions. You won’t be radioactive or pass radiation to anyone else. If you’re sexually active with someone who can get pregnant, it’s important to use birth control (contraception) during your radiation therapy.

You might have concerns about how cancer and your treatment can affect your sex life. Talking with your healthcare provider about your sexual health can be hard, but it’s an important conversation to have. They may not discuss this with you unless you bring up your questions and concerns. While you may feel uncomfortable, remember that most people in cancer treatment have similar questions. We work hard to make sure everyone in our care feels welcome.

MSK also has sexual health programs to help you manage the ways your cancer or cancer treatment affect your sexual health. Our specialists can help you take action and address sexual health or fertility issues before, during, or after your treatment.

For more information about your sexual health during cancer treatment, read the resource Sex and Your Cancer Treatment. You can find it online or ask your healthcare provider for a copy. The American Cancer Society also has resources about sexual health issues during cancer treatment titled Sex and the Adult Male with Cancer and Sex and the Adult Female with Cancer. You can search for them at www.cancer.org or call 800-227-2345 for a copy.


Emotional health

Cancer diagnosis and treatment can be very stressful and overwhelming. You may feel:

  • Anxious
  • Afraid
  • Alone
  • Ambivalent
  • Angry
  • Depressed
  • Helpless
  • Frustrated
  • Nervous
  • Numb
  • Worried

When you or someone you love has a serious illness, all these kinds of feelings are expected. You might also worry about telling your employer you have cancer or about paying your medical bills. You may worry about how your family relationships may change, how cancer treatment will affect your body, or if you’ll continue to be sexually attractive. You may worry that the cancer will come back. It’s normal and OK to worry about all these things. We’re here to support you.

Ways to cope with your feelings

Talk with others. When people try to protect each other by hiding their feelings, they can feel very alone. Talking can help the people around you know what you’re thinking. It might help to talk about your feelings with someone you trust, such as your spouse or partner, close friend, family member, chaplain, nurse, social worker, or psychologist.

You may also find it helpful to talk with someone who’s going through radiation therapy or who has been through a similar treatment. You can do this through our Patient and Caregiver Support Program. Call 212-639-5007 to learn more about this service.

Join a support group. Meeting other people with cancer will give you a chance to talk about your feelings and learn from others. You can understand how other people cope with their cancer and be reminded you aren’t alone.

We recognize all diagnoses and all people experiencing cancer aren’t the same. We offer support groups for people who share similarities in diagnoses and identity. For example, you can join a support group for people with breast cancer or a group for LGBTQ+ patients. To learn about MSK’s support groups, visit www.mskcc.org/vp or talk with your radiation oncologist, radiation nurse, or social worker.

Try relaxation and meditation. You might try thinking of yourself in a favorite place and breathing slowly while paying attention to each breath or listening to a soothing music or sound. For some people, praying is another way of meditation. These kinds of activities can help you feel relaxed and calm. Visit www.mskcc.org/meditations to find guided meditations lead by our Integrative Medicine providers.

Exercise. Many people find that light activity, such as walking, biking, yoga, or water aerobics, helps them feel better. Talk with your healthcare provider about types of exercise you can do.

We all have our own way of dealing with difficult situations. Generally, we use whatever has worked for us in the past. But sometimes this isn’t enough. We encourage you to talk with your doctor, nurse, or social worker about your concerns.

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After Your Treatment

Please be sure to keep your follow-up appointments with your radiation oncologist. He or she will evaluate your response to treatment. You may have blood tests, x-rays, and scans during these visits. Before coming, write down your questions and concerns. Bring this and a list of all your medications with you. You can also call your doctor or nurse at any time after your treatment is completed, or in between follow-up visits, if you have any questions or concerns.

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Contact Information

If you have any questions or concerns, talk with a member of your radiation therapy team. You can reach them Monday through Friday from 9:00 am to 5:00 pm at the numbers listed below.

Radiation oncologist: _____________________
Phone number: _________________________

Radiation nurse: ________________________
Phone number: _________________________

After 5:00 pm, during the weekend, and on holidays, call 212-639-2000. Ask for the radiation oncologist on call.

If you have any questions or concerns, talk with a member of your radiation therapy team. You can reach them Monday through Friday from 9:00 am to 5:00 pm. After 5:00 pm, during the weekend, and on holidays, call 212-639-2000. Ask for the radiation oncologist on call.
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Support Services

You can find many of these support services on the Internet. If you don’t have a computer or don’t know how to use the Internet, check with your local public library or community center.

MSK support services

Counseling Center
Many people find that counseling helps them. We provide counseling for individuals, couples, families, and groups, as well as medications to help if you feel anxious or depressed. To make an appointment, ask your healthcare provider for a referral or call the number above.

Integrative Medicine Service
MSK’s Integrative Medicine Service offers many services to complement (go along with) traditional medical care, including music therapy, mind/body therapies, dance and movement therapy, yoga, and touch therapy.

Nutrition Services
MSK’s Nutrition Service offers nutritional counseling with one of our certified dietitians. Your dietitian will review your current eating habits and give advice on what to eat during and after treatment.

Patient and Caregiver Peer Support Program
212-639-5007You may find it comforting to speak with someone who has been through a treatment similar to yours. You can talk with a former MSK patient or caregiver through our Patient and Caregiver Peer Support Program. These conversations are confidential. They may take place in person or over the phone.

Resources for Life After Cancer (RLAC) Program
At MSK, care doesn’t end after active treatment. The RLAC Program is for patients and their families who have finished treatment. This program has many services, including seminars, workshops, support groups, counseling on life after treatment, and help with insurance and employment issues.

Tobacco Treatment Program
If you want to quit smoking, MSK has specialists who can help. Call for more information.

Virtual Programs
MSK’s Virtual Programs offer online education and support for patients and caregivers, even when you can’t come to MSK in person. Through live, interactive sessions, you can learn about your diagnosis, what to expect during treatment, and how to prepare for the various stages of your cancer care. Sessions are confidential, free, and led by expert clinical staff. If you’re interested in joining a Virtual Program, visit our website at www.mskcc.org/vp for more information.


Radiation therapy support services

American Society for Therapeutic Radiology and Oncology
A group of radiation oncology professionals that specializes in treating patients with radiation therapy. Provides detailed information on treating cancer with radiation and contact information for radiation oncologists in your area.

External support services

There are many other support services available to help you before, during, and after your cancer treatment. Some offer support groups and information, while others can help with transportation, lodging, and treatment costs.

For a list of these support services, visit www.mskcc.org/pe/external_support_services. You can also talk with an MSK social worker by calling 212-639-7020.

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Questions to Ask Your Healthcare Provider

Before your appointment, it’s helpful to write down the questions you want to ask your healthcare provider. Examples of questions you can ask are listed below. Write down the answers during your appointment so you can review them later.

What kind of radiation therapy will I get?

How many radiation treatments will I get?

What side effects should I expect during my radiation therapy?

Will these side effects go away after I finish my radiation therapy?

What kind of late side effects should I expect after my radiation therapy?

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