Radiation therapy - what to expect

About radiation therapy


Radiation therapy is the treatment of cancer using beams of high-energy waves called radiation.

The radiation used for cancer treatment comes from special machines or from radioactive substances. Radiation therapy machines aim specific amounts of the radiation at tumors or parts of the body where there is/was disease to kill cancer cells or keep them from spreading.

Information on your treatment plan is available through your Radiation Oncology Team.

Radiation affects all cells. Healthy cells are able to repair themselves through normal cell function. Unhealthy cells, such as cancer cells, are not able to repair after radiation.

Watch our detailed education video

Take a 12.5 minute tour to learn what happens during radiation treatment for cancer.This is a detailed education video to better prepare patients for radiation therapy mixed with patient stories.

What are the types of radiation therapy?

External radiation therapy
External radiation therapy is given from a special machine (called a linear accelerator). The patient never becomes radioactive.
Internal radiation therapy
Internal radiation therapy is when the source of radiation is placed inside the body near the cancer cells. The length of time the implant is in place depends upon the type of implant received.

Why is radiation given?

Radiation therapy is used to treat cancer and a few non-cancerous diseases. Radiation treatments can be used to:

  • Treat cancer by killing, stopping, or slowing the growth of cancer cells
  • Shrink tumors to reduce pain, pressure, or other side effects if a cure is not possible. The term palliative is often used to describe this process.

Radiation therapy is often used with other treatments

Radiation may be used before, during, or after surgery. It is used to shrink the tumor to a smaller size before surgery or to kill any remaining cancer cells after surgery. Sometimes doctors give radiation during surgery so the radiation can be directed right at the cancer cells without having to go through the skin.

Radiation can also be used with chemotherapy. Sometimes radiation is given to shrink the tumor before or during chemotherapy so the medicines will work better. Other times the chemotherapy helps the radiation treatment work better than chemotherapy alone.

What should I expect on my first visit

When radiation therapy might be of help, a family doctor, surgeon or medical oncologist (a doctor who specializes in treating cancer with medicines) will refer patients to a radiation oncologist.

The doctor will first review your medical records and X-rays. A physical exam will be done.

The doctors will then talk to you about his/her findings and decide how you should be treated. If radiation will help you, the staff will schedule the needed studies to develop a treatment plan. This is sometimes referred to as simulation.

During simulation, the therapist takes X-rays of the part of your body to be treated to help decide how the radiation will be given. Using the X-ray as a guide to the treatment site, the therapist uses a marker to outline the treatment area on your skin. This area is often called a “treatment port” or “treatment field”. These marks are very important. They act as a map of the treatment area and the therapist uses them each day to guide your treatment. Sometimes after a few treatments, tiny permanent dots (called tattoos) can be used to replace the painted marks on your skin.

Treatment planning

After the imaging studies, the treatment team develops a plan to give treatment. The goal includes sending a high dose of radiation to the tumor while sparing the normal tissues.

What to expect during radiation treatments

Treatments are usually given five days a week for six to seven weeks. If the goal of treatment is palliative (to control symptoms) treatment will last 2-3 weeks in length. Using many small doses (fractions) for daily radiation, rather than a few large doses, helps to protect the healthy cells in the treatment area. The break from treatment on weekends allows the normal cells to recover.

It is very important to finish all sessions of radiation therapy. It is important not to miss or delay treatments because it can lessen how well the radiation kills tumor cells.

The radiation therapy technologist (RTT) may ask you to change into a gown before treatment. It is a good idea to wear clothing that is easy to pull down, adjust, or remove when coming for treatments.

During the actual treatment sessions you will be in the treatment room between 10-30 minutes. You will be receiving radiation for 1-2 minutes of that time.

You will be asked to lie on a hard, moveable bed. The RTT will use the marks on your skin to exactly position the machine and table. In some instances, special blocks or shields are used to protect normal organs. You may be positioned using special holders, molds or boards.

It is extremely important to remain still during the radiation treatments. Breathe normally during treatments. You do not need to hold your breath. You will not feel anything during the treatment. Radiation is painless. You will not see, hear, or smell radiation.

The RTT will leave the room. You will be alone in the room, but there is a closed circuit TV and an intercom in the room. The RTT can see and hear you at all times. If you think you need to move, tell the therapist at once. The machine can be turned off.

The radiation machine is quite large. The machine can move around you and it will make noises. The RTT can control the movement of the machine from outside the room. The therapist will be checking the machine at all times. A physicist checks the accuracy of the machine often.

You may possibly have several types of tests or checks during your treatment course. Port films (an X-ray taken by the treatment machine) are taken to make sure that positioning is exactly where it should be. Some types of radiation treatment areas will require weekly blood tests to check the blood cell counts.

The radiation oncologist will meet with you about once a week. This visit is to check on how your body has been reacting to treatment. Be sure and tell your doctor any symptoms you are having.

Side effects

The side effects of radiation therapy are mainly confined to the area being treated. Fatigue (tiredness) is a side effect that can be experienced by anyone undergoing radiation. Get plenty of rest and sleep when you need to. Sometimes several shorter naps or breaks may be more helpful than a long rest period. Mild or light exercise, such as walking, may help decrease fatigue.

The degree of tiredness will be different in each person. Some people with desk jobs continue to work as usual. Others feel best if they work half days. Persons who do heavy labor may need to take time off during radiation therapy and for a few weeks after treatment is completed.

Some side effects come on quickly. These effects are called “acute”. They happen while you are receiving treatment. Late effects are changes in the body that happen as a result of radiation. They do not show up until a few months to years after radiation is done. Ask your doctor about what the possible side and late effects are for your type of radiation therapy.

You may have different side effects depending on what type of cancer you have and where on the body radiation treatment is being delivered to.

Effects on the skin

Radiation can cause the skin to become red, itchy or both. You may want to:

  • Wear loose, soft, cotton clothing over the area being treated.
  • Avoid stiff or starched clothing near the area being treated.
  • Do not put anything but mild soap (such as Dove) and lukewarm water on the skin in the treated area, unless the doctor or nurse says that it is safe to do so.
  • Wash the area gently with your hand. Do not use a washcloth over the treated area.
  • Do not scratch, rub or scrub the area.
  • Do not put a heating pad or an ice pack on the area.
  • Avoid girdles or any tight clothing in the treatment area.
  • Do not use moisturizers/lotion 2 hours before your radiation treatment.
  • Do not allow the treatment area to be in direct sunlight for at least one year past the last treatment.

Cranial (brain) radiation

Brain swelling is a common side effect that will go away. This swelling may cause an increase in your brain tumor symptoms. Medicines called steroids are often used to reduce brain swelling.

Hair loss—hair loss will begin after about two weeks of treatment. Your hair will begin to return 2-3 months after treatments have ended. A change in color and/or texture may occur. Soft scarves or hats are attractive and comfortable as a cover for the head until hair grows back. With higher doses of radiation to the brain, hair loss can be permanent.

Head and neck radiation

Radiation treatment of head and neck tumors cause some side effects. Dry mouth is caused because the glands that make saliva (spit) are in the area of radiation. Saliva can become thick and you may have less saliva. The decrease in saliva can cause a greater chance for cavities in the teeth. You will need to be seen by a dentist before starting treatment. The dentist may need to remove any teeth that might give you problems. The dentist may also make molds for use with fluoride treatments to prevent cavities. It is very important you follow all of the dentist’s recommendations. Newer techniques of radiation delivery can minimize some of these side effects. It may be helpful for your dentist to speak with your radiation oncologist before any dental work is done, during or after the period of treatment.

What can be done about the side effects?

  • Rinse your mouth with a salt and soda solution every 1-2 hours. (In a quart of water, put a teaspoon of salt and ½ teaspoon of baking soda). This is the most important thing you can do to reduce mouth problems during radiation.
  • Avoid mouthwash that contains alcohol.
  • If you wear false teeth, ask your doctor if you can still wear them during treatment.
  • Eat soft, moist foods. Put gravy and sauces on foods to make them easier to swallow.
  • Avoid foods with sharp edges such as crackers or chips.
  • Eat when you feel hungry, even if it is not meal time.
  • Do not use alcohol-based after-shave. Use an electric razor for shaving.
  • Ask your doctor about special prescription mouthwashes to reduce mouth symptoms and make swallowing easier.
  • Ask your doctor or nurse about using liquid dietary supplements.
  • Carry a container of water with you so you can take frequent sips.
  • Sugar free gum or candy may help relieve dry mouth.

Chest radiation

There are several side effects from radiation therapy to the chest. Some people notice a “lumpy” feeling when they swallow. This is due to swelling of the esophagus (food tube), part of which is in the treatment area. Drinking lots of liquids during meals can help this problem. Eating soft, moist non-spicy foods can help also. Chewing food very well and swallowing only small amounts will lessen the lumpy feeling also. If it is severe, or keeps you from eating, ask the doctor about medicine that may help.

Some people have more coughing and mucus production during treatment. Shortness of breath is also common. If you begin to notice these symptoms, talk to the doctor or nurse.

Things that may help breathing problems:

  • Keep a humidifier or vaporizer close to you at all times to keep phlegm thinner so it can be coughed up easier. (Rinse humidifier bowl with a solution of 1/3 cup vinegar and 1 cup water, every day).
  • Drink plenty of liquids to help in thinning phlegm.
  • Sit with arms on a table in front of you. Lean on a table that has pillows placed on it for more comfort.
  • Raise the head and chest while lying in bed. Wedge pillows can be purchased for this purpose.
  • During times of shortness of breath, try inhaling through the nose and exhaling through pursed lips very slowly.
  • Avoid irritants, such as smoke.

Breast radiation

The two side effects that most often affect patients undergoing radiation therapy for breast cancer are fatigue and skin changes. The skin may become red after two weeks of treatment. In rare instances, the skin can blister and peel. These reactions will go away a few weeks after the last radiation treatment. Some women will also have breast swelling and tenderness. A few months after treatments are finished some women will notice the skin is tan or slightly darker than it was before treatment. Some women notice the breast is a different size and/or is firmer than before treatment.

What can be done about side effects?

  • Do not wear a bra, if at all possible. Or wear a bra over a soft white tee shirt. Surgical and sports bras are acceptable.
  • Do not wear bras with under wires.
  • Ask your doctor/nurse if you can use deodorant.
  • Avoid heavy exercise that will produce a lot of sweat. This can cause skin irritation.

Upper abdomen (stomach) radiation

Radiation to the upper area of the abdomen may cause a sick feeling in the stomach and loss of appetite. Some people may feel queasy for a few hours after their radiation treatment.To manage sick feelings due to radiation treatment:

  • If you feel queasy before treatment, try a snack of dry toast, crackers and a clear beverage, such as apple juice or a carbonated beverage.
  • If queasy feeling after radiation, try not eating for a few hours before treatment and a few hours after.
  • Eat six small meals a day, rather than three larger meals.
  • Avoid greasy, fried, fatty or spicy foods.
  • Drink and eat beverages and foods when they are at or below room temperature.
  • Choose foods that have a mild aroma or smell.
  • Ask your doctor for medicine to help control the sick feeling if it becomes a problem or it keeps you from eating.

Radiation to the pelvis

Radiation therapy to the pelvis (area below the navel) can cause bowel and bladder problems in some patients, including:

  • Urinating more than usual
  • Burning with urination
  • Loose, watery stools
  • Rectal burning/irritation
  • Rectal bleeding
  • Vaginal discharge in females
  • Sexual and/or problems getting pregnant or fathering a child

Management of Side Effects during Pelvic Radiation Therapy

  • Do not eat raw fruits, vegetables or whole grains
  • Eat small, frequent meals
  • Do not drink caffeine or alcohol
  • Drink lots of fluids (2 quarts a day)
  • Drink cranberry juice as part of fluid intake
  • Ask your doctor or nurse for medicine if you have painful urination or to lessen frequent loose stools
  • Use birth control to prevent pregnancy
  • Your doctor may prescribe medicines that decrease the number of bowel movements.

When to call your doctor

Weight loss

  • If you lose five pounds or more

Difficulty breathing, nausea, or vomiting

  • Cannot eat or drink for 12 hours
  • Vomiting three times an hour for 3 or more hours
  • Cannot take your medicine because you are sick to your stomach


  • Temperature taken in the mouth over 100.5 or chills
  • Bowel movements
  • Six or more loose, watery bowel movements in 24 hours
  • Blood on the toilet tissue or in the toilet bowl water


  • Oozing, painful skin

Follow-up after radiation treatment

Most radiation therapy patients will need follow-up care for the rest of their lives. You will need to visit your radiation oncologist or nurse for regular check-ups after your treatment is done. At the check-ups your doctor will talk to you about how you are feeling, check you to see how well the radiation worked and look for any signs of cancer. The doctor will also talk with you about any side or late effects you may be having.

It is important to let your doctor or nurse know if you have any of the following symptoms:

  • Pain that does not go away
  • Any new bumps, swelling, rashes, bruises, or bleeding
  • Feeling sick to your stomach, vomiting, diarrhea, constipation, or changes in appetite
  • Weight loss without a reason
  • Fever, cough, or sore throat that does not go away
  • Any other symptoms that bother you
Last reviewed: 
August 2018

Interested in using our health content?