Radiation treatment

Radiation treatment is sometimes called radiotherapy or radiation therapy. It is used to destroy cancer cells or prevent them from reproducing.

On this page, you can find the following information:

What is radiation treatment?

Radiation treatment is the use of high-energy radiation to destroy cancer cells or prevent them from reproducing. Radiation treatment only affects the part of the body at which the beam(s) is aimed, so is very localised. Radiation treatment is sometimes called radiotherapy or radiation therapy.

About half of all people with cancer need radiation treatment at some point in their illness. For some types of cancer this is the main treatment. It might also be used in combination with surgery, chemotherapy or hormone therapy.

Types of radiation treatment

Radiation treatment can be given in two ways: from outside the body (external radiation) or inside the body (internal radiation or brachytherapy). External beam radiation treatment is the most common method - a radiation beam is focused from a machine outside the body onto the area affected by the cancer.

With internal radiation treatment (brachytherapy), radioactive material is put into your body, on or near the cancer. In some cases, a combination of both forms of radiation treatment is used.

Why radiation is used to treat cancer

In the treatment of cancer, radiation is used for different effects.

  • To cure cancers, often in addition to other cancer treatment.
  • To shrink a tumour, so that surgery is more effective (neoadjuvant radiation treatment).
  • To treat any cancer cells remaining after surgery (adjuvant radiation treatment)
  • To control cancers and to keep cancers at bay for a long time.
  • To relieve symptoms; for example, to reduce pain or a cough. This is called palliative treatment

The treatment team

A team of health professionals will provide your treatment and care. They include:

  • Radiation oncologist – a doctor who specialises in the use of radiation in the treatment of cancer. This doctor is responsible for your overall treatment. There will be other doctors working in a team with your specialist to care for you.
  • Registrars and house surgeons – doctors who are part of your medical team.
  • Medical physicists – responsible for quality assurance of radiation equipment and software
  • Radiation therapists – therapists who plan and deliver your treatment.
  • Oncology nurses – nurses who specialise in the care of patients with cancer.
  • Dietitians.
  • Social workers.

External radiation

A course of external radiation treatment is given over a number of days or weeks. Each treatment is known as a ‘fraction’. Fractions are usually given daily from Monday to Friday with a rest at the weekend to help normal cells recover.

External radiation delivers a beam of radiation by a treatment machine called a linear accelerator. A superficial therapy machine is used for the treatment of skin cancer. The choice of treatment machine depends on the type of cancer and the affected part of your body. Some machines are better at treating cancers near the surface of the skin, while others are used to treat cancers deeper in the body.

While you lie still, the machines are moved up and down and around you so that the radiation can be directed at the tumour from different angles and it is similar to having an x-ray taken. During this treatment you do not see or feel anything.

Planning your treatment

The process of planning external beam radiation treatment is complex and might take several weeks to complete. It is one of the most important parts of your radiation treatment. After your planning session, check with staff on how long it will be before your treatment starts. A treatment plan will be designed just for you. It will give the required dose of radiation to the cancer but will spare as much normal tissue as possible. This will help reduce the side effects.

If you are having treatment to your pelvis, you might be sent instructions on how to prepare your bladder and bowel for this treatment. The first part of treatment planning is called simulation, sometimes referred to as a 'marking up' session.

Simulation part of planning process

Before you start a course of external radiation treatment you will require at least one visit to the cancer centre to work out the exact position you will lie in during your treatment (a simulation). A simulator – a machine similar to a treatment machine or a CT scanner – is used for this.

During planning, the treatment team considers many factors, including:

  • what type of radiation to use
  • the size and shape of the radiation field
  • patient position as well as machine positioning
  • how much radiation is to be delivered for each treatment
  • how many beams of radiation.

This is all done on computers using the information from simulation, a CT scan, and other tests you have had.

This process of simulation can take 30 to 60 minutes and is a much longer process than each individual treatment. It is important that you lie still in the same position when you have your treatment. You might have an ‘immobilisation device’ to help you keep still. This can range from special supports to a face mask made of plastic for people requiring treatment to the head and neck area.

The machine is set to treat exactly what is to be treated with a ‘safety margin’. Once the position of the beam is worked out, your skin or the mask will be marked. This may require a tattoo which is a permanent marking, but occasionally can be removed later. It can be helpful to have a family member or friend with you during simulation and planning.


Dosimetry is the process where the doctor and the radiation therapist decide on the amount of radiation you need and the best ways to aim it at the cancer with the least effect on normal tissue (making a treatment plan). They base this on the size of the tumour, how sensitive the tumour is to radiation, and the ability of the normal tissue in the area to tolerate the treatment.

How long is a course of treatment?

External radiation is usually given in a number of treatments (or fractions). The number of treatments is not necessarily related to the seriousness of the cancer. It depends on several factors, including your general health, and the site and type of cancer being treated. You might want to allow time before and after treatment each day, as delays in your appointment might occur.

If a high dose of radiation is required, it is usually given on 4 or 5 days a week for 5 to 7 weeks. If a quick response is required, such as to relieve a cough or pain, stop bleeding or reduce swelling, a shorter course is more likely to be given. The total amount of time spent in the treatment room is usually 10 to 20 minutes. The machine is only turned on after the therapists have made sure you are in the correct position.

The actual treatment usually takes a very short time - a few minutes at most. External radiation is usually given as an out-patient. If you are already in hospital, you will be taken to the radiation treatment department daily.

Will external radiation make me radioactive?

No. External radiation treatment does not make you radioactive. It is safe to be with your children, family and friends both throughout the treatment and after the treatment has been completed.

Internal radiation or brachytherapy

Internal radiation (brachytherapy) involves placing an implant of radioactive seeds or wires, such as caesium or iridium into the body, close to the cancer. Brachytherapy is used to give higher doses of radiation exactly where the cancer is, without having to go through healthy tissue.

You will be advised by your doctor and nurse about any limitations or side effects from this treatment. Your doctor might suggest treatment using brachytherapy alone or in combination with external radiation treatment.

Brachytherapy for gynaecological cancer

High dose rate (HDR)

In brachytherapy for gynaecological cancer, hollow plastic or metal tubes (applicators) are inserted into the vagina. A machine feeds small 5mm radioactive metal rods (the source) into the tubes. The tubes are put in position under a general anaesthetic, but for some treatments a spinal anaesthetic or light sedation might be used instead.

Each treatment takes about 10 to 20 minutes. There might be a number of treatments to complete the course. In some New Zealand centres, treatment is given over several days. Once the radiation treatment has finished, the applicators are removed by a doctor or nurse. This might be after each treatment or only at the end of the full course of treatment.

Brachytherapy for prostate cancer

Low dose rate (LDR)

In brachytherapy for prostate cancer, tiny radioactive seeds are inserted permanently into the prostate gland. This form of treatment can be successful for small tumours which are located within the gland. Depending on your cancer, prostate brachytherapy might be combined with external beam therapy.

For about two months after treatment, children and women who are pregnant (or who might be), should not stay very close to you for long periods of time. However, it is safe for them to be in the same room as you. If you are resuming sexual intercourse, condoms should be used for two weeks after your seed implantation. This is in case a seed accidentally moves and is ejaculated in the semen.

Low dose brachytherapy is currently only available in the private hospital system.


Radioisotopes are given as liquids, in capsules that are swallowed, or as a drink; or by injection into a vein (as an intravenous injection). The most common type of radioisotope treatment is radioactive iodine. It is used to treat tumours of the thyroid gland, and is given as capsules. The same safety precautions are taken with this type of treatment as for other types of internal radiation treatment.

Any radioactive iodine that is not absorbed by the thyroid will be passed from the body in sweat and urine. You need to drink plenty of fluids during your treatment as this helps to flush the iodine out of the body. The amount of radiation in your body will be checked regularly and as soon as it falls to a safe level, after a few days, you will be able to go home.

You might need to take some special precautions for a short time after going home – and might need to avoid young children and pregnant women for a short time. The hospital staff will explain this to you.

Radioactive iodine does not usually cause side effects, but you might feel very tired for a few weeks after having this treatment.

Radioisotope treatment for secondary bone cancer

Radioisotope treatment can also be given if certain types of cancer have spread to the bones (secondary cancer in the bone). A radioisotope is injected into a vein and is taken up into the bone so that the radioactivity works against the cancer cells. The aim of this treatment is to reduce pain and slow the growth of cancer in the bone. This is usually given as an outpatient. (Secondary bone cancer is often treated with a short course of external radiation.)

Before you go home you will be given some simple advice to follow, as your urine and blood will be slightly radioactive for a few days. You might feel tired for a few weeks. You will have regular blood tests as you might become anaemic.


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Credits: Health Navigator Editorial Team. Last reviewed: 07 Jan 2015