Radiotherapy for bowel cancer

What is radiotherapy?

Radiotherapy uses high-energy X-rays, electron beams or radioactive isotopes to attack cancer. Radiotherapy causes cancer cell death by damaging the chromosomes in the cell so that the cells cannot multiply.

Radiotherapy is a local treatment -- aimed directly at the cancer. Aside from its use as a single treatment, radiotherapy has been shown to enhance the effects of chemotherapy. It can be used in combination with chemotherapy to shrink a tumour before it's removed. For tumours that can't be removed, radiation can reduce or alleviate the pain, bleeding or blockages caused by these tumours.

Which bowel cancer patients should have radiation?

The role of radiation in bowel cancer isn't well defined. There are a few for whom the addition of local or regional radiation may improve control of the disease and lengthen survival.

Radiotherapy plays a much more important role in treating bowel cancer where it can be used to reduce the size of a tumour before local excision (removal) of the cancer.

Radiotherapy is also used as adjuvant therapy (additional therapy) with chemotherapy for bowel cancer to improve survival rates.

In some cases, such as if the tumour is small or you are very old or ill, radiation alone can be used to treat the tumour.

If bowel cancer returns, it is very debilitating and often associated with chronic pelvic pain. Therefore, pelvic radiation can be administered before or after bowel cancer surgery, or both to help relieve the pain and other symptoms associated with the disease.

What types of radiation are available?

Successful radiotherapy depends on delivering the proper amount of radiation to the cancer in the best and most effective way. There are several types of radiotherapy.

External beam radiotherapy

External beam radiotherapy is the most common form of radiotherapy. Before treatment begins, detailed planning or simulation is performed. During simulation, a team of specialists, including a radiation oncologist, will use measurements from scans and calculations to determine the precise location to aim the radiation. They will tattoo small, non-permanent dots on your body to indicate where to target the beam to ensure they radiate the same location at every treatment. This process may take several hours.

During the treatment, you will be positioned on a table so that a beam from a machine outside the body may be aimed at the tumour. The radiation treatment itself lasts only a few minutes, but it may be given five times a week for several weeks, and sometimes a couple of times per day for several weeks.

Internal radiotherapy (also known as brachytherapy)

Internal systemic radiotherapy involves injecting radioactive isotopes either into a vein or into an organ. One of the most common types of systemic radiotherapy is radioactive iodine (I-131), which is given for some types of thyroid cancer. Another type of systemic radiotherapy is the use of strontium-89. This isotope is used to treat cancer that has spread to the bone.