What is Radiation Therapy? - Definition, Types & Side Effects

Instructor: Danielle Haak

Danielle has a PhD in Natural Resource Sciences and a MSc in Biological Sciences

What is radiation therapy? This lesson will outline what it is, what it's used for, different types, and the possible side effects from this treatment.

What Is Radiation Therapy?

Radiation therapy is a type of treatment used to attack cancer cells and shrink tumors. Radiation therapy uses X-rays, gamma rays, and charged particles. Radiation therapy may be delivered from outside the body or through an internal treatment such as radioactive iodine. It's estimated that about half of all cancer patients will receive some type of radiation therapy during the treatment of their cancer.

Types of Radiation Therapy

As mentioned, radiation therapy can be delivered either externally or internally. When determining the appropriate treatment type, the type and size of the cancer, its location in the body and proximity to vital organs, the patient's general health and medical history, and the combination of all treatment types are all considered.

When therapy is delivered externally, it's delivered by an external-beam radiation therapy machine, also known as a linear accelerator. This machine uses photon beams and specialized computer software to target the area of interest. Treatments usually occur daily for several weeks. Other external delivery options may include intensity-modulated radiation therapy, image-guided radiation therapy, tomotherapy, stereotactic radiosurgery, proton therapy, or other charged particle beams.

A patient undergoing external radiation therapy
External-beam radiation therapy

When therapy is delivered internally, it's called brachytherapy. A radiation source may be placed directly in a tumor (interstitial brachytherapy) or near a tumor (intracavitary brachytherapy). These radioactive isotopes are placed in small packets, or 'seeds,' that are inserted into the desired location in the patient. These packets usually degrade completely on their own over time and do not need to be manually removed. The radioactivity of the packet is determined ahead of time and may be classified as low-dose or high-dose.

Another type of internal radiation therapy is systemic radiation therapy. With this approach, the patient swallows or is injected with a radioactive substance.

Side Effects of Radiation Therapy

It's well known that radiation is generally something we want to steer clear of, so what are the side effects of a treatment like this? In order for radiation to be considered, the potential benefits outweigh the negative effects of treatment. Some people do not experience any side effects at all! The most common side effects include skin conditions, such as itching, blisters, dryness, and peeling. Fatigue is also another side effect and does not improve with rest. Possibly the worst side effect is the development of a secondary cancer as a result of the radiation exposure!

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