Radiation Therapy

What is radiation therapy?

Radiation therapy, also called radiotherapy, is a type of cancer treatment. Radiation therapy uses radiation, usually in the form of high-powered X-rays, to destroy cancer cells. Radiation therapy can be delivered externally (called external beam radiation therapy or EBRT) or internally.

Radiation therapy can be given on its own or with other cancer treatments, such as surgery or chemotherapy. The type of radiation therapy you receive will depend on the type of cancer you have and other factors.

A healthcare professional who specializes in radiation therapy is called a radiation oncologist. They will decide if radiation therapy will be of benefit to you and they will design a radiation treatment plan tailored to your condition. This includes giving a radiation dose that will kill the cancer cells without damaging nearby healthy tissue.

How does radiation therapy work?

Radiation therapy delivers high-energy radiation, such as X-rays or gamma rays, to a targeted area. The radiation damages the cancer cell’s DNA and its ability to deliver instructions telling it how to divide and grow. When the ability to grow and divide is disrupted, it causes them to die. Radiation therapy is targeted, meaning the aim is to minimize damage to nearby healthy tissues. Treatment usually takes several weeks to complete before the cancer cells are fully affected. Radiation therapy is also used to shrink tumors or to relieve cancer symptoms, such as pain (depending on the stage of the cancer).

Are there different types of radiation therapy?

External beam radiation therapy (EBRT) and internal radiation therapy (high dose rate brachytherapy) are the main types of radiotherapy. Both deliver radiation which destroys a cancer cell’s DNA and its ability to grow and divide, causing cancer cells to die and the tumor to shrink.

External beam radiation therapy (EBRT)

EBRT is the most commonly used type of radiotherapy. A linear accelerator machine outside of the body directs high-energy radiation beams at the tumor. Energy is usually in the form of photons, electrons, or protons. A radiation oncologist will carefully design a treatment plan to precisely target the tumor while avoiding nearby healthy tissue.

Types of EBRT include:

3D conformal radiation: This uses CT scans and a computer to create a 3D model of the tumor. With the model as a guide, radiation beams are directed to the cancer site while sparing healthy tissue.

Intensity-modulated radiation therapy (IMRT): An advanced form of radiation therapy which uses lots of beams of radiation which vary in intensity. Higher doses of radiation are delivered to the tumor while lower doses are delivered to healthy tissue.

Arc-based radiotherapy (VMAT): This is a type of IMRT which delivers energy beams of varying intensities in an arc-like rotation pattern. Radiation is delivered faster than traditional IMRT.

Image-guided radiotherapy (IGRT): A type of EBRT in which a low-dose cone beam CT (CBCT) obtains images before each treatment, helping to deliver more precise radiation.

Stereotactic radiosurgery: This therapy uses high dose, focused radiation in people with small brain tumors.

Stereotactic body radiation therapy (SBRT): Focused, high doses of radiation are given to destroy tumors outside of the brain. It can destroy tumors with surgical accuracy without the need for surgery.

Internal radiation therapy

Internal radiation therapy delivers radiation inside the body. This means it is delivered close to cancer cells. It is used to treat small breast tumors, prostate tumors, uterine tumors, cervical tumors, or tumors in the head or neck.

If radiation is delivered via a solid source, it is called brachytherapy. If radiation is delivered via a liquid, it is called systemic therapy. Radiation may be swallowed or injected in a vein, where it travels through the blood to find cancer cells and destroy them.

Radionuclide therapy (also called radioimmunotherapy) is one type of liquid internal radiation therapy, in which a radioactive protein finds specific cancer cells and attaches to them. It then releases radiation to kill the cancerous cells.

When is radiation therapy given?

Radiation therapy can shrink tumors, kill cancer cells and relieve cancer symptoms. It may be the only treatment given, or it may be given to:

• Shrink tumors before surgery or other cancer treatments are given. This is called neo-adjuvant therapy.
• Destroy cancer cells that may remain after surgery. This is called adjuvant therapy.
• Kill cancer cells that have returned after a previous treatment.
• To destroy noncancerous (benign) tumors which are causing symptoms.

What are the benefits of radiation therapy?

Radiation therapy has been used for many years. It is an effective and reliable type of cancer treatment. Radiation therapy can destroy cancer cells or help other types of cancer treatment to work more effectively (depending on the type of cancer).

Radiation therapy can also relieve cancer symptoms and is an important part of palliative care.

What are the side effects/risks of radiation therapy?

The side effects of radiation therapy usually only affect the part of your body which is directly receiving radiation. These may include:

• Nausea
• Fatigue
• Diarrhea
• Vomiting
• Skin irritation
• Headaches
• Mouth sores
• Hair loss
• Reduced appetite
• Pain when you swallow
• Abdominal cramps/bloating
• Burning feeling in the chest/throat
• Burning sensation when peeing
• Needing to pee frequently
• Urgent feeling to have a bowel movement

Radiation therapy is usually spread over a number of treatment sessions. This gives healthy tissue time to recover and reduces side effects. Your radiation oncologist will discuss side effects with you and ways to help you manage them.

While radiation therapy is an effective treatment for many types of cancer, it may increase the likelihood of developing a different cancer in the future. However, for most people, the benefits of radiotherapy outweigh the risk. Your radiation oncologist will discuss the benefits of treatment against the risks with you.