What is radiotherapy?

Radiotherapy, or radiation therapy, is a form of cancer treatment that uses radiation to shrink tumours or kill cancer cells in a small, targeted area. Radiotherapy most often uses X-rays, but may also involve protons or other types of energy such as gamma rays.

Radiotherapy, chemotherapy and surgery are the 3 most common approaches to treat cancer. They are often used together, such as in concurrent chemo-radiation or in sequence e.g. radiotherapy followed by surgery.

How it works

Radiation therapy kills or slows the growth of cells by destroying their DNA. Once the genetic material is damaged, cancer cells stop dividing and start dying.

Radiation therapy takes effect over a period of time. It may take days or weeks of radiation before the cancer cells are destroyed. Even after radiotherapy has ended, the cancer cells will continue to die for weeks or months.

Types of radiotherapy

There are 2 main types of radiation therapy.

External beam radiation therapy

In external beam radiation therapy, a machine aims radiation at your cancer without contact with your body. It may move around you and direct beams to a specific part of your body from different angles.

External beam radiation therapy includes:

Internal radiation therapy

In internal radiation therapy, a source of radiation is placed inside your body. The source of radiation can be:

  • Solid. This type of radiotherapy is known as a brachytherapy. In a brachytherapy, a small radioactive pellet or seed is implanted in your body near the tumour. This allows higher doses of radiation to be given to specific areas of the body.
  • Liquid. Unlike external beam radiotherapy and brachytherapy which are local treatments specific to an area, this is a systematic therapy that affects your entire body. The liquid source travels in your bloodstream to tissues throughout your body, seeking out and killing cancer cells. You may need to swallow the liquid source, or receive it via an intravenous line or injection.

Your doctor will recommend a suitable type of radiotherapy for your treatment based on factors, including:

  • The type of cancer
  • The size of the tumour
  • Where the tumour is located, including its proximity to radiation-sensitive tissues
  • Your general health and medical history
  • Whether you will have other types of cancer treatment
  • Other factors, including your age and other medical conditions

Difference between radiotherapy and other treatment options

What is the difference between radiotherapy and chemotherapy?

While radiotherapy uses high-energy particles or waves to kill cancer cells, chemotherapy uses drugs to treat cancer. Chemotherapy is a systemic treatment as its drugs spread throughout your body, whereas radiotherapy is usually localised at a specific body area.

What is the difference between radiosurgery and radiotherapy?

The difference between radiosurgery and radiotherapy has to do with the intensity and duration of the radiation treatments.

In stereotactic radiosurgery, radiation is delivered at a very high intensity, in one single dose, to a small area.

In stereotactic radiotherapy, radiation is delivered at different times, at lower intensities to larger areas. This allows the healthy tissue time to recover between treatment sessions.

What is the difference between radiotherapy and proton therapy?

Proton therapy is a newer type of radiotherapy that uses a different energy source. While radiotherapy more commonly uses X-rays, proton therapy uses energy from positively charged particles (protons) to kill cancer cells.

Why do you need radiotherapy?

Radiotherapy is used to:

  • Shrink a tumour to make it easier to remove through surgery, or to ease symptoms in palliative care.
  • Destroy any cancer cells that were not successfully removed during surgery.
  • Reduce the chance of a cancer relapse.

What are the risks and complications of radiotherapy?

Radiation not only destroys cancerous cells, they also damage healthy cells. Recent radiotherapy techniques such as 3D conformal radiation therapy have reduced this risk by improving the accuracy of beams to target the tumours.

Still, there will be damage to healthy cells and side effects due to the damage. Side effects depend on where your body is exposed to radiation and how much radiation is used.

Below are some of the sides effects for different body parts exposed to radiation.

Any part of the body:

  • Fatigue
  • Temporary or permanent hair loss
  • Skin changes


  • Diarrhoea
  • Nausea and vomiting
  • Urinary and bladder changes


  • Blurry vision
  • Headache
  • Nausea and vomiting


  • Swelling
  • Tenderness


  • Cough
  • Difficulty breathing
  • Difficulty swallowing

Head and neck:

  • Changes to the mouth and sense of taste
  • Difficulty swallowing
  • Less active thyroid gland

Pelvis and rectum:

  • Bladder irritation
  • Diarrhoea
  • Sexual and fertility problems
  • Urinary issues

Most side effects are manageable and will subside once your treatment has ended.

There is a lifetime dose limit to the amount of radiation an area of your body can safely receive in your lifetime. Your doctor will factor this in when recommending radiotherapy. However, if one area of the body has already reached the limit, another area might still be able to receive radiotherapy if the 2 areas are far apart.

Why choose Parkway East Hospital?

Parkway East Hospital is the preferred private hospital in the east of Singapore. Our team of radiation oncologists and nursing professionals will support you throughout your radiotherapy. We provide holistic, customised treatment in a caring environment to help you focus on your recovery from cancer.

Estimated cost

Private healthcare can be affordable. Use our Hospital Bill Estimator to determine the estimated cost of this procedure. If you have hospital insurance, find out how you can use your insurance.

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