What is radiation therapy?

Radiation therapy is the use of high energy beams to kill cancer cells or prevent them from reproducing. All cells within the radiation field may be affected but normal cells repair themselves better than cancer cells.

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

Four goals of radiation therapy are:
1) To cure cancers.
2) To help other cancer treatments. It may be given before or after the main treatment, for example, to:

• shrink a tumour so that surgery is more effective;
•  treat any cancer cells remaining after surgery.

This is called adjuvant radiation therapy.

3) To control cancers. Cancers can be controlled for varying periods of time by radiation therapy.
4) To relieve symptoms. Radiation therapy may also be given to relieve your symptoms, for example, to lessen pain. This is called palliative treatment.

Making decisions about treatment

You may be offered a choice of treatments, or your doctor may suggest no treatment for now. If you are offered a choice, the following questions may help you to make a decision:

• What are the advantages and disadvantages of radiation therapy for me?
• Are there any other treatments I can have instead?
• Will radiation therapy cure me or simply control the cancer?
• What difference would it make if I waited?
• Can I have a second opinion?
• How long will my treatment last and how often will I have to have it?
• Will I have to stay in hospital?
• What side effects can I expect?

Before you see the doctor, it may help to write down your questions.
It may also help to:

• take notes during the session
• take a family member or friend with you
• tape record the session.

About radiation therapy

Radiation therapy can be given either from outside the body (external radiation) or from within (internal radiation). External radiation uses x-rays from an x-ray machine or linear accelerator. For internal radiation, radioactive material is placed in or close to the tumour.

The treatment team

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

• Radiation oncologist - a doctor who specialises in the use of radiation in the treatment of cancer. The doctor decides on and supervises your treatment. There may be other doctors working in a team with your specialist to care for you 
• Radiation therapist - the technologist who prepares you and gives you your treatment
• Oncology nurse - a nurse who specialises in the care of patients with cancer.

External radiation

External radiation is administered electronically by a linear accelerator or superficial therapy machine. 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.

The machines are moved up and down and around you so that the radiation can be directed at the tumour from different angles. This form of treatment is painless and it is similar to having an x-ray taken.

Planning

Before you start a course of radiation you will require at least one visit to the cancer centre to work out the exact position you will lie or sit in during your treatment. To help you keep still and stay in the same position it may be necessary to use supports or make an individualised mask or shell. You will be set up in the proposed treatment position, as if to mimic or to simulate a treatment. X-rays and measurements will be taken using a machine that gives x-ray or CT scans, or a combination of both.

This whole process of simulation can take 20–60 minutes and is a much longer process than each individual treatment. It is common practice to tattoo a few tiny dots of ink into the skin to leave small permanent marks to assist both in treatment set up and as a long-term reference.

Planning the actual treatment requires identification by the doctor of the target to be treated, the dose to be delivered, and identification of any structures that need protection from radiation. The planners can then work out the best way to treat you. They need to consider many factors including:

• what type of radiation to use
• the size and shape of the radiation field
• what positions and how many different positions of the machine
• how much radiation is to be delivered from each treatment.

This is all done on computers using the information from simulation and other tests you may have had.

How long is a course of treatment?

External radiation is usually given in a number of small treatments (or fractions). The number of treatments is not 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.

if a high dose of radiation is required, it is usually given on four or five days a week for 5-7 weeks, as the body can tolerate the treatment better this way and a more effective anti-cancer dose can be given.  If a quick response is required, such as to relieve 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 10-20 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 therapy department daily.

Will external radiation make me radioactive?

No. External radiation therapy 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

Internal radiation (also known as brachytherapy) involves placing an implant of radioactive material such as caesium or iridium into the body, close to the cancerous tissue. You will be advised by your doctor and nurse about any limitations or side effects from this treatment.

Radiation therapy with implants is most commonly used to treat cancers of the uterus, cervix and prostate and sometimes mouth and neck.

Your doctor may suggest treatment using brachytherapy alone or in combination with external radiation therapy.

How long will the implant stay in my body?

Brachytherapy (or internal radiation) may be given by a Low Dose Rate (LDR) system or a High Dose Rate (HDR) system. LDR treatments are generally given over hours to days, often from 1–6 days, depending on the situation and whether it is combined with external treatment. HDR brachytherapy is given in minutes, but is usually repeated a number of times (fractions).

Tubes may be used to determine the placing of the radioactive source and sometimes these tubes are left in position between treatments; sometimes the positioning of tubes is repeated at each session. With some cancers (eg. prostate cancer) an implant may be left in place permanently. Other inserts (eg. iridium) may be in place for a matter of minutes.

Will the implant be painful?

You may feel some discomfort, but should not experience severe pain or feel ill during implant therapy. If your implant is held in place by an applicator, you may feel uncomfortable. If this is the case tell your doctor because there may be a medication to relieve the discomfort.

Will internal radiation make me radioactive?

While your implant is in place it may send some radiation outside your body. This is why hospitals do not allow children under 18 or pregnant women to visit people with implants.  Once the implant is removed, all traces of radioactivity disappear.

If you have a permanent implant, you may need to stay in the isolated room in the hospital for the first few days while the radiation is most active.

The implant becomes less radioactive each day, so by the time you are ready to go home, radiation in your body will be very weak. You will be checked thoroughly before you are allowed to go home.

Related topics

What side effects might occur from radiation therapy? See Radiation therapy side effects

What if a man has prostate cancer? For more information on radiation therapy for prostate cancer, see Prostate cancer treatment

What does that term mean? See Cancer glossary

Original material provided by the Cancer Society of New Zealand, 2005. Reviewed by everybody, September 2008.