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Radiotherapy: A guide

Radiation therapy is a common treatment for many forms of cancer. Here is a quick look at when and how it is used, and its side effects.

Radiation therapy, also known as radiotherapy, is one of the most common treatments for cancer. It can be applied alone or in combination with other treatments such as surgery, chemotherapy or medication.

Radiation therapy uses high-energy particles or waves such as X-rays, gamma rays, electron beams or protons, to damage or destroy cancer cells. Doing so kills the genetic material within the cancerous cells resulting in their disability to grow and spread.

Doctors who specialise in radiation therapy – radiation oncologists – are trained to administer just the right amount of radiation a patient can receive. This is done on a case-by-case basis, depending on the patient, type of cancer, and its location. Their goal is to deliver the dose of radiation to the tumour site as precisely as possible, in order to protect the healthy cells surrounding it.

When it is used

Radiation therapy is administered either curatively or palliatively.

Curative radiotherapy is given with the intention to cure; meaning doctors are hopeful that this form of treatment (whether alone or combined with other types of treatment) can eliminate the tumour entirely, damage it before it spreads, or shrink it to be able to remove it surgically.

Palliative radiotherapy is administered to alleviate symptoms caused by growing tumours. It is meant to reduce patient suffering and improve quality of life. Radiation oncologists typically use this form of therapy to shrink tumours that grow close to the spine, oesophagus or the lungs, all of which affect a patient’s quality of life.

Different types of therapy

There are three main ways radiotherapy is delivered – externally, internally and systemically. How this is decided depends on many factors such as the size and location of the tumour, as well as the patient’s age, health and medical history.

External radiation therapy makes use of a machine to direct radiation beams directly to the site of the tumour. There are six different ways to do this:

1. Intensity-Modulated Radiation Therapy (IMRT) where radiation beams are precisely manipulated to conform to the shape of the tumour to minimise damage to surrounding healthy tissue.
2. Image-Guided Radiation Therapy (IGRT) where images of the tumour are acquired to plan and guide individualised treatments.
3. 3D Conformal Radiation Therapy (3D-CRT) uses a simulation to generate 3D images of the tumour, which allows highly conformed radiation beams to be delivered in higher doses while significantly reducing radiation exposure to other cells.
4. Radiosurgery consists of tightly focused beams of radiation from multiple directions that deliver a strong dose of radiation to the tumour site.
5. Stereotactic Radiation Therapy relies on detailed imaging, computerised 3D treatment planning and precise treatment set-up to deliver doses with extreme accuracy.
6. TomoTherapy® delivers doses of radiation slice-by-slice and can be used for multiple targets simultaneously.
    

Internal radiation therapy uses a form called Brachytherapy where radiation is delivered from inside the body by implanting radioactive materials into or adjacent to the tumour.

Systemic radiation therapy involves the patient swallowing or being injected with radioactive drugs that travel through the bloodstream in order to target the cancer cells.

Safety and side effects

In order to optimise patient safety, radiation oncologists and their teams work closely with primary doctors to determine the best course of action for each patient. Every treatment plan is tailored to the individual’s needs; these include type and stage of cancer, size and location of tumour, and the patient’s medical history.

While radiation therapy has been used successfully to treat cancer for over a century, it does not come without side effects. These may vary from patient to patient but fatigue appears to be chief among them.

Early (or acute) side effects include tiredness and skin soreness around the treatment area. But these usually wear off gradually as treatment concludes.

Late (or chronic) side effects typically occur after treatment ends, but not all patients experience this. This may be due to several factors such as a patient’s medical history, genetic makeup and lifestyle habits.

Written by Charmaine Ng