Radiation Therapy

What Is Radiation Therapy ?

Radiation therapy is a cancer treatment that uses high doses of radiation to kill cancer cells and shrink Tumor. Radiation therapy may be used alone or with other types of cancer treatment, including surgery, chemotherapy or both.

How Does Radiation Therapy Works Against Cancer ?

At high doses, radiation kills cancer cells or slows their growth by damaging their DNA. cancer cells whose DNA is damaged beyond repair stop dividing or die. When the damaged cells die, they are broken down and removed by the body.

Radiation therapy does not kill cancer cells immediately. It takes days or weeks of treatment before DNA is damaged enough for cancer cells to die. Then, cancer cells keep dying for weeks or months after radiation therapy ends.

Types Of Radiation Treatment

There are two main types of radiation therapy, external beam and internal beam radiation therapy.

The type of radiation therapy that you may be advised will depend on many factors like the type and size of tumor, its location, the nearby normal structures to the tumor, the general condition, associated comorbidities, ongoing or previous cancer treatment( if any),

External Beam Radiation Therapy(Ebrt)

EBRT comes from a machine that aims radiation at your cancer. The machine is large and might make some noise. It can move around you without touching you, and delivers radiation to a part of your body from many directions. External beam radiation therapy is a local treatment, which means it treats a specific part of your body. For example, if you have cancer in your throat, you will have radiation only to your neck, not to your whole body.

Internal Radiation Therapy

Internal radiation therapy is a treatment in which a source of radiation is put inside your body. The radiation source can be solid or liquid.

Internal radiation therapy with a solid source is called brachytherapy. In this type of treatment, seeds, ribbons, or capsules that contain a radiation source are placed in your body, in or near the tumor. Like external beam radiation therapy, brachytherapy is a local treatment and treats only a specific part of your body. With brachytherapy, the radiation source in your body will give off radiation for a while.

EBRT is commonly used to treat many types of cancer. Whereas brachytherapy is most often used to treat cancer of the Head and Neck, Breast, Cervix, prostate, and eye.

There is another type of radiation called systemic radiation therapy called radioactive iodine, or I-131, which is most often used to treat certain types of Thyroid cancer.

Another type of systemic radiation therapy, the targeted radionuclide therapy or molecular radiotherapy is used to treat some patients who have advanced prostate cancer or gastroentero pancreatic neuroendocrine Tumor. Radiation beams used in external radiation therapy come from three types of particles: photons, electrons, and protons.

What Are The Different Types Of EBRT ?

The main aim of radiation therapy in all types is to deliver the highest prescribed dose of radiation to the tumor while sparing the normal tissue in the surrounding area.

Conventional (2D) radiation therapy refers to the old techniques of radiation therapy where treatment would be planned by defining a limited number of beams with the boundaries delineated on orthogonal x-rays of the patient. Two-dimensional (2D) radiotherapy consisted of a single beam from one to four directions. It has been largely replaced by other highly conformal radiation techniques now. Although 2D radiotherapy is now rarely used, it still has a role in Palliative treatments which use generous margins and where the simplicity of the planning process allows same-day treatment.


3D CRT, or three-dimensional conformal radiation therapy, is an advanced technique that incorporates the use of imaging technologies to generate three-dimensional images CT, MRI, PET-CT of a patient’s tumor and nearby organs and tissues. The use of three-dimensional images in the treatment planning process mainly distinguishes 3D CRT from conventional radiation therapy. With the help of detailed information through imaging, a higher and more effective dose of radiation can be delivered directly to the tumor and simultaneously the amount of radiation received by the surrounding healthy tissues can be significantly reduced.


Intensity modulated radiation therapy (IMRT) This is a more complex form of radiation. With IMRT, the intensity of the radiation is varied within each field unlike conventional 3D-CRT, which uses the same intensity throughout each beam. IMRT targets the tumor and avoids healthy tissue better than conventional 3D-CRT.

Image-guided radiation therapy (IGRT) This refers to the practice of using daily images of each treatment field to confirm patient positioning and make sure the target is in the field. These daily images are compared to the images used to plan treatment. IGRT allows your doctor to make each treatment field smaller. This allows better targeting of the tumor and helps reduce damage to healthy tissue.

Volumetric modulated arc therapy (VMAT) is a novel radiation treatment similar to IMRT technique. This technique delivers the radiation dose continuously as the treatment machine rotates. This technique accurately shapes the radiation dose to the tumour while minimising the dose to the organs surrounding the tumour.

Stereotactic radiosurgery(SRS) is the use of focused, high-energy beams to treat small Tumor with well-defined edges in the Brain and central nervous system. It may be an option if surgery is too risky due to your age or other health problems or if the tumor cannot safely be reached with surgery. GammaKnife is a type of stereotactic radiosurgery.

Stereotactic radiation therapy (SRT) This is similar to stereotactic radiosurgery, but it is used for small, isolated Tumor outside the brain and spinal cord, often in the Liver or lung. It may be an option when you cannot have surgery due to age, health problems, or the location of the tumor. As in stereotactic radiosurgery, stereotactic body radiation therapy uses special equipment to hold you still during treatment. It delivers a highly precise beam to a limited area.

Proton beam therapy This treatment uses protons rather than x-rays. A proton is a positively charged particle. At high energy, protons can destroy cancer cells. The protons go to the targeted tumor and deposit the specific dose of radiation therapy. Unlike with x-ray beams, there is very little radiation dose beyond the tumor. This limits damage to nearby healthy tissue. This therapy is relatively new and requires special equipment. It is available only at a limited center.

Tomotherapy type of intensity-modulated radiation therapy (IMRT), also called helical tomotherapy. In this type radiation is aimed at a tumor from many different directions. The patient lays on a table and is moved through a donut-shaped machine. The radiation source in the machine rotates around the patient in a spiral pattern. Before radiation, a 3D image of the tumor is taken. This helps to find the highest dose of radiation that can be used to kill tumor cells while causing less damage to nearby tissue.

Intraoperative radiation therapy (IORT) Intraoperative radiation therapy (IORT) This treatment delivers radiation therapy to the tumor during surgery using either external-beam or internal radiation therapy. IORT allows surgeons to move away healthy tissue in advance. This treatment is useful when vital organs are close to the tumor.

Radioimmunotherapy This is a type of systemic therapy. It uses monoclonal antibodies, which are proteins that are attracted to very specific markers on the outside of cancer cells, to deliver radiation directly to the Tumor. Because the treatment uses these special antibodies, there is less effect on surrounding normal tissue. An example is ibritumomab (Zevalin), which is used in the treatment of some lymphomas.

What To Expect When Having External Beam Radiation Therapy ?

How Often Is EBRT Given ?

Most people have external beam radiation therapy once a day, five days a week, Monday through Friday. Radiation is given in a series of treatments to allow healthy cells to recover and to make radiation more effective. The total number of sessions depends on the type of cancer you have, the intent of your treatment, the radiation dose, and the radiation schedule.

What Happens Before Radiation Therapy Treatment ?

Each radiation treatment plan is customised to meet a patient's individual needs, but there are some general steps. You can expect these steps before beginning treatment:

Your radiation oncologist will review your medical records, perform a physical exam, and recommend tests. You will be explained about. You can have a detailed discussion with your doctor about any concerns that you might have in your mind.

Following the discussion if you agree to go ahead with the radiation treatment, the below procedure would be followed,

Simulating and planning treatment Your first radiation therapy session is a simulation. This means it is a practice run without giving radiation therapy. To identify the tumor location imaging scans like CT, MRI, and X-ray would be done.

Depending on the treatment area, a small mark on your skin is made. This will help your team aim the radiation beam at the tumor. An immobilization device using Tape, Foam sponges, Headrests, Molds, Plaster casts would be customised for you. This is to ensure the same position throughout treatment.

For example, for head and neck cancer treatment, a thermoplastic mask is molded to your face and secured to the table. It gently holds your head in place.

A mask fitted to your face helps make sure that you are in exactly the same position for each treatment.

Credit: National Cancer Institute

What Usually Happens During A Radiation Treatment Session ?

First you would be asked to change into a hospital gown or robe or expose the treatment area depending on the treatment site.

You will be sent to the treatment room where you will receive radiation. The temperature in this room will be very cool as the radiation machine needs to be maintained under a specific cool temperature.

Depending on the treatment site you will be made to lie down and the position is adjusted on the couch. The radiation therapy technician will use the dots on your skin and body mold or face mask, to help place you in the right position. You will see some colored lights pointed at your skin marks. These lights are harmless and help the therapist position you for treatment. This is to ensure the exact positioning.

You need to stay still so the radiation goes to the exact same place each time. Any kind of movement is to be strictly avoided as it may interrupt with the treatment delivery.

Usually you will get radiation for 1 to 5 minutes, this time would vary depending on the technique used to plan your radiation treatment. All this while, you can breathe normally.

Once the position is set, the technician will leave the room just before your treatment begins. The therapist watches you on a TV screen or through a window and talks with you through a speaker in the treatment room. If you feel sick or are uncomfortable at any given point, make sure to tell the therapist. The radiation machine can be stopped at any time in such events. You will hear the radiation machine and see it moving around, but you won't be able to feel, hear, see, or smell the radiation.

Most visits last from 30 minutes to an hour, with most of that time spent placing you in the correct position.

What To Wear For Your Radiation Treatment ?

It is advisable to wear loose comfortable breathable soft fabric like that of fleece or cotton.

During the treatment you need to take off the clothes to expose the treatment area or to change into the hospital gown, depending on the site of treatment, so choose clothes that are easy to take off. Avoid clothes that are tight, tubs against the skin and causes friction. Do not wear any jewellery, do not apply any perfumes, alcohol based ointments or creams over the treatment area.