Definition & Overview

Radiation therapy is one type of treatment that is prescribed for cancer patients. The high concentration of energy that is released in radiation therapy is enough to kill cancer cells without having to destroy healthy cells, making it an essential part of cancer treatment.

Who Should Undergo & Expected Results

A radiation oncologist, the doctor that specializes in using radiation for cancer treatment, will prescribe the ideal radiation treatment for the patient following a consideration of factors listed below:

  • The type of cancer the patient has
  • The size of the tumor
  • The location of cancer
  • If normal, healthy tissues would be in the way of the radiation
  • How far has cancer spread out in the body
  • The patient’s overall health condition and medical history
  • If radiation therapy is the sole treatment or if it will be part of an adjuvant program
  • Other medical conditions that are needed to be considered


Radiation therapy can be used as main, adjuvant or palliative cancer treatment.

  • Main cancer treatment – Radiation therapy can be used as the main cancer treatment in which it will become the first line of defense and by itself, it can cure cancer. It can be used to shrink a tumor until it disappears and at the same time, kill the cancer cells present in the area.

  • Adjuvant cancer treatment – Radiation therapy can also be used in combination with other forms of cancer treatment. For example, a patient who has a massive tumor typically undergoes a surgery first to have the tumor removed or shrunk. Radiation therapy will then be performed afterward to clear the area from remaining cancer cells. The patient can also have radiation therapy with chemotherapy either at the same time or in succession. In some cases, radiation therapy can be used with both surgery and chemotherapy.

  • Palliative cancer treatments – Radiation therapy can also be used to keep patients more comfortable when curing them is no longer an option. In most cases, radiation therapy is used to shrink tumors that have grown in parts of the body that can no longer be operated on and are causing the patient considerable pain or interferes with the body’s ability to function normally, like if it’s near the esophagus, the tumor can prevent the patient from eating and drinking.

How Does the Procedure Work?

There are two types of radiation therapy procedures and each differs in the way that radiation is administered to the body.

The first type is called external (or external beam) radiation therapy and it involves the use of a machine, like a linear accelerator or LINAC, to deliver the high–energy waves to the tumor. The treatment requires several number of low-dose radiation treatments scheduled over a certain period. Usually, it takes five days a week with two days off to allow for normal cell recovery. The procedure consists of the following steps:

  • A planning or simulation session where the radiation oncologist will review the patient’s medical history and may refer to CT or MRI scans to pinpoint the areas to focus the radiation on. These imaging results are then programmed into the computer and will be used during the treatment process. In some cases, a mold or cast is necessary and custom-made for the patient to keep them immobile during the treatment. Other times, small dots made from semi-permanent ink or tattoo-like permanent dots are used to mark the treatment area. Finally, the doctor will then decide the treatment schedule, the number sessions, and the dosage of radiation for each session.

  • On the day of the treatment, the patient enters the room where the machine is and will be asked to lie down on the treatment table. The radiation therapist will operate the machine from a shielded room. The machine will move around the table and the patient to reach all the treatment areas. The process will take about 15-30 minutes, including the time the machine is set up and the patient is positioned.

  • Once the procedure is over, the radiation therapist will return to the room to help the patient get off the table.

  • The process is repeated every day until the planned number of sessions has been completed.


The second type of radiation therapy is called internal radiation therapy or brachytherapy. It involves the implantation of a radioactive source into a body cavity (intracavitary) or into or near the tumor (interstitial). The radiation is contained in “seeds” that are injected into the body through catheters. It can be performed either under local or general anesthesia. The isotopes in the seeds naturally give off radiation as they die and that is the radiation that kills the cancer cells. In permanent brachytherapy, the seeds remain in the body but don’t cause any harm and the radiation source is removed afterward. In temporary brachytherapy, the path through which the radiation implants are placed is not removed until after the treatment has been completed. This allows the easy, repetitive procedure to be done smoothly every time the radiation source has to be implanted. Once the treatment is over, this tube or applicator is removed.

Possible Complications and Risks

When dealing with radiation, there’s always a threat of being radioactive especially with brachytherapy. While the implant is still inside the body, the patient is radioactive and may be required to stay in the hospital with minimum interaction with other people. Once the implant is removed, the patient is no longer radioactive and can resume normal activities.

In permanent brachytherapy, the patient will be radioactive for as long as the radiation source is active. However, the radiation levels are low but care must be exercised around pregnant women and young children.

There are also side effects that a patient will experience but they differ depending on the type of cancer that he has, the area where the treatment is focused, and if there are other treatments happening at the same time.

References:

  • Zemen EM, Schreiber EC, Tepper JE. Basics of radiation therapy. In: Niederhuber JE, Armitage JO, Doroshow JH, et al., eds. Abeloff's Clinical Oncology. 5th ed. Philadelphia, PA: Elsevier Churchill Livingstone; 2013:chap 27.

  • National Cancer Institute. Radiation therapy and you: support for people who have cancer. Available at: http://www.cancer.gov/cancertopics/coping/radiation-therapy-and-you.

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