Radiation Therapy

Radiotherapy Mohali


External beam radiation therapy is also called external radiation therapy or teletherapy. A machine directs a beam of radiation through the skin to the tumour and a small amount of normal surrounding tissue. This approach can treat larger areas of the body or more than one area, such as the tumour and nearby lymph nodes. Most people who have radiation therapy for cancer receive external beam radiation.

External beam radiation therapy:
  • Doesn’t hurt
  • Doesn’t make the person radioactive
  • Can’t be seen, felt or smelled


Occasionally, treatments are given more than once a day or every other day. This depends on:
  • The type of cancer
  • The person’s overall health
  • The total dose
  • The fractionation schedule
  • Whether other types of treatment are given at the same time

When radiation therapy is given to relieve symptoms caused by advanced cancer (palliative radiation therapy), the course of treatment is shorter, such as a few days or weeks

The radiation oncologist (a doctor who specializes in treating cancers using radiation therapy) decides on the total dose of radiation that will be given to kill cancer cells and spare normal cells as much as possible. This dose is divided into a number of smaller doses called fractions. Fractionation schedules can vary.
  • Standard (conventional) fractionation
  • The most common schedule for external beam radiation divides the total dose of radiation into several smaller doses or fractions. Treatments are usually given once a day, 5 days a week, and may last for several (about 3–8) weeks.
  • Hyperfractionation
  • With hyperfractionated radiation, the daily dose of radiation is given over 2 or more sessions each day. The total period of time to complete the treatment schedule is not changed. By using multiple smaller doses of radiation, a higher overall dose can be given.
  • Accelerated fractionation
  • With accelerated radiation therapy, the total dose of radiation is given over a shorter period of time by giving the same dose of radiation more than once a day. Accelerated fractionation does not change the total radiation dose.
  • Hypofractionation
  • With hypofractionated radiation therapy, fewer radiation treatments are given. This is done by giving either a short course of daily treatments or by giving fewer large doses (sometimes just a single treatment).
  • Boost
  • For some tumours, radiation may be given to a small area after the regular radiation treatment is finished. This radiation boost may be given externally or internally. It is used to reduce the risk of recurrence in a certain area. Radiation boosts can also be used to treat the tumour or area around the tumour with a higher dose than nearby normal tissues would tolerate.

Getting external beam radiation therapy

External beam radiation therapy is given in the radiation therapy department of a cancer treatment centre, usually on an outpatient basis. Having external beam radiation therapy is similar to having an x-ray. Before external beam radiation treatment, the person may need to change into a hospital gown. They also need to remove anything metal, such as jewellery, zippers or diaper pins, in the treatment area (treatment field). Anything with tight elastic, such as socks or diapers, should be loosened or removed.

During the treatment session:

  • The radiation therapist positions the person on the treatment table based on the simulation.
  • Marks or tattoos made on the skin or alignment lasers help locate the treatment area.
  • Immobilization devices, forms, foam wedges or rolls may be used to ensure the person is in the proper position and lies still during the treatment.
  • Special shielding blocks may be placed between the radiation machine and certain parts of the body to help protect healthy tissue and organs.
  • Once the person is positioned and the equipment is set up properly, the radiation therapist leaves the treatment room.
  • Parents are not allowed in the treatment room when children have treatment because they would be exposed to radiation. Depending on the treatment centre’s policy, parents may be allowed to watch their child through a window into the treatment room. Parents may be asked to wait in the waiting room until the treatment is complete.
  • The radiation therapist controls and turns on the machine from the next room. The therapist can watch the person through a window or a monitor. They can communicate through an intercom.

The radiation oncologist monitors the person’s progress throughout the course of treatment and adjusts the dose or length of treatment as necessary. The radiation therapy team often take special x-rays (port films) during treatment. They review these x-rays to ensure the treatment beam stays on target. Sometimes blood tests, x-rays or other tests are done during the course of treatment to see how the tumour is responding to treatment.

Occasionally, radiation therapy treatments may need to be stopped temporarily if side effects are severe. Missed treatments can be made up later.

Safety precautions

External beam radiation doesn’t make a person radioactive. It is safe to be around other people, including children, right after treatment.

Activity during treatment

Some people can work and continue to do their regular leisure activities while receiving radiation therapy. Others find they tire easily and need to rest more.

Simulation for external beam radiation therapy

Simulation is a planning session done before the first external beam radiation treatment is given. It is done to make sure the radiation is aimed at exactly the same area each time treatment is given. Simulation is usually done in one session and may take anywhere from 15 minutes to an hour or more.

A machine called a simulator is used to set up the treatment plan and choose the treatment area. A simulator is not a treatment machine. The most common type of simulator used is a CT (computed tomography) simulator. It can take images or scans, which give the healthcare team a picture of the part of the body to be treated. A conventional x-ray simulator may also be used in some situations. These images help the radiation therapy team decide where and how to direct the radiation.

Simulation for external beam radiation therapy

The dose of radiation is precisely calculated and prescribed in units called grays (Gy). The total dose is usually divided into several smaller daily doses (called fractions). The dose of radiation and the number and length of treatments depend on:
  • The type of cancer
  • How sensitive the tumour is to radiation therapy (radiosensitivity)
  • Tumour size
  • Tumour location
  • The stage of the cancer
  • The amount of tissue to be radiated
  • The ability of surrounding normal tissue to tolerate radiation
  • Whether other cancer treatments have been or will also be given


The position that the person should be in to receive the treatment is chosen during the simulation. The person is positioned the same way each time a treatment is given.

Skin markings

The skin may be marked to act as a map and help ensure that each radiation treatment is targeted to the same area. The skin may be marked with a pen or ink, and the person must be careful not to wash off these temporary markings. Tiny permanent tattoos – about the size of a freckle – may also be used.

Immobilization devices

Sometimes immobilization devices are made to help the person stay in the same position and lie still for treatment. Forms, moulds, pads or other devices are made from plastic, foam, plaster or other materials. Immobilization devices are specially made to fit the person’s shape. Marks to pinpoint the treatment area may be made on the mould rather than the skin.

Shields and blocks

Special shields or lead blocks may be used to protect or guard normal tissue or organs from radiation. Blocks are usually made specifically for each person. Just before treatment is given, the shields or blocks are placed between the radiation therapy machine and the areas of the body that need protection.