There are two forms of radiation therapy:

1. 1. External beam radiation therapy - the beam of radiation is focused by an external machine onto the treatment area

2. 2. Internal radiation therapy (such as brachytherapy) - a radioactive substance is placed in or close to the cancerous tissue.

1. External beam radiation therapy is the more commonly used form of radiotherapy. A machine called a linear accelerator is usually used in external beam radiation therapy to emit X-rays within a specific energy range. Other machines are also available, with these using other forms of energy, including electrons, protons (as in proton therapy) and gamma rays, or a combination. The idea is that different forms of external beam radiation therapy have specific effects that best suit the particular tumor.

2. Brachytherapy involves introducing low-energy radioactive metal that has a short range. This means it exerts its effects in a localized area to disrupt nearby cancer cells.

Highly radioactive material can be temporarily placed in or near the tissue - held in a tube, for example, and then removed, or less radioactive brachytherapy seeds can be left in place permanently, with their radioactivity gradually dropping off to zero. Between these two types of brachytherapy, there are also radioactive wires that may be left in place for a number of days.

Radioactive liquid is used in other forms of internal radiation therapy. This liquid is swallowed or received by injection. Radioactive iodine is used as a treatment for thyroid cancer, and bone cancer may be treated with radioactive forms of strontium, phosphorus or radium.

When is radiation therapy used?

Cancers that can be particularly suitable for radiation therapy aimed at curing the disease are those that are well-defined and confined. This allows the whole area of cancerous tissue to be targeted by the radiation. In contrast, some forms of cancer - lymphoma - can be treated with total body irradiation.

Palliative radiation therapy

Radiation therapy can also be used to reduce symptoms and tumor size, lessen the pain caused by tumours - palliative radiation therapy. While the cancer will not be cured by the radiation treatment, it can help to stop the formation of further painful bone cancers, and help to reduce the pain caused by weakened bone (by strengthening it and preventing further weakening).

Radiation therapy for cancer may be deployed:

• Alone - against prostate cancer or a tumour of the larynx, for example, when radiation may be preferable to surgery

• Alongside surgical treatment - before a cancer operation (to shrink the tumour), during it, or afterward (to reduce the risk of incomplete removal of cancer cells)

• With drug treatment, chemotherapy - a combination that can reduce the need for surgery.

4.1. Fill in the gaps with the following words.

Painless, a linear accelerator, radiation therapy, treatment, symptoms, palliative

1. External beam radiation therapy is typically administered using……….

2. Radiation therapy can also be used to reduce ……, caused by tumor growth, for example.

3. Radiation therapy is not always suitable for ………use.

4. The response of a tumor to ………. is also related to its size.

5. Before……… , a CT scan is often performed to identify the tumor and surrounding normal structures.

6. Radiation therapy is in itself ……….