Radiation Therapy

Chavy Dworkind
Mar 16, 2021
3 min read

Chavy Dworkind

Published Tuesday, March 16, 2021

You have probably heard of radiation therapy or radiotherapy. But did you know that there are two main types of radiation therapy? First, there is external beam radiation therapy and second, there is internal beam radiation therapy. Let’s find out how radiation therapy works and specifically, how the two aforementioned types or radiation therapy compare.

Image by str.llnl.gov via https://devarajaniyengar.wordpress.com/2016/09/29/external-and-internal-radiotherapy-in-the-treatment-of-cancer/.

External Beam Radiation

How does it work?

According to the National Cancer Institute, “External beam radiation comes from a machine that aims radiation at your cancer” (National). This treatment targets a specific part of the patient’s body, depending on where the cancer is. Thus, external beam radiation is a local treatment. As a result, the patient mainly receives radiation in the affected area, leaving the rest of the patient's body is relatively protected from the radiation.

Image by Tera Vector, Cancer Today via https://www.cancertodaymag.org/Pages/Spring2020/New-Guidelines-for-Radiation-Therapy-in-Pancreatic-Cancer.aspx.

There are three types of beams used in external radiation therapy:

Photons: This is the most common beam used. Additionally, photon beams are used in x-rays but in much lower doses (National). Photon beams tend to fragment and scatter small pieces of themselves along their journey through the body. The fragments can go into healthy body tissue, even once they have reached the tumour. Photon beams can travel deep into the body.
Protons: Protons are the positively charged components of atoms, found in an atom’s nucleus. The proton beams are aimed directly at the cancer. Additionally, proton beams differ from photon beams because they do not spread radiation in the body once they reach the tumour. Therefore, it is probable that proton radiation exposes less healthy tissue to radiation, than photon radiation. Similar to photon beams, proton beams can travel deep into the body.
Electrons: Electrons are the negatively charged components of atoms, found surrounding the atom’s nucleus. Different from photon beams and proton beams, electron beams cannot travel very deep into the body. As a result, electron beams are primarily used for tumours that are superficial, meaning on or near the surface of the body.

There are many ways in which external beam radiation can be administered to a patient. Each type is similar because they all use a computer to help them determine the most effective and safe treatment plan based on the images and the location of the tumour in the body.

The following are several types of external beam radiation therapy:

3-D conformal radiation therapy
Intensity-modulated radiation therapy
Image-guided radiation therapy
Tomotherapy
Stereotactic radiosurgery
Stereotactic body radiation

External beam radiation is the most common form of radiation therapy (Understanding).

Internal Beam Radiation

How does it work?

Internal beam radiation involves placing radioactive substances inside the body (implants). Furthermore, the radioactive implants can be either permanent or temporary. One way that internal beam radiation differs from external beam radiation is that a larger dose of radiation can be administered in internal radiation therapy (Internal).

Note: Internal radiation therapy is also known as brachytherapy (Getting).

Image by Treatment Process and Effectiveness via https://lungevity.org/sites/default/files/illustrations/brachy-seeding.png.

Permanent Implants

Small capsules the size of a grain of rice containing radioactive material are placed in or near the cancer. The radiation mainly occurs in close proximity to the capsules. However, some radiation can leave the body (Understanding). Therefore, other people may need protection when they are near the patient so that they don’t receive the radiation therapy too! Patients who recently received permanent implants may be advised to stay away from small children and pregnant women to avoid spreading the radiation to those individuals (Getting). The permanent implants are the most radioactive near the time of the implantation. However, permanent implants become less radioactive with each passing day. After several weeks or months, they will not be radioactive anymore which is why it is okay to leave permanent implants inside the patient’s body (Getting).

Temporary Radiation Therapy

Temporary implants remain in the body for a few minutes, hours, or days before they are removed. Temporary radiation is administered with needles, catheters (tubes inserted in the body), or special applicators. When patients receive temporary radiation therapy for more than a few minutes, they will often be shown to a room where visitors are not allowed. This is to prevent visitors from potentially receiving radiation from the patient’s temporary implants (Understanding).

Conclusion

In this post, we discussed the use of radiation therapy to treat cancer. External beam radiation can be administered using photon beams, proton beams, or electron beams. Less commonly used is internal beam radiation which can be administered via permanent internal transplants or temporary internal transplants containing radioactive matter. The goal of all radiation therapy is to kill cancer cells or to slow their growth.

Works Cited

“External Beam Radiation Therapy for Cancer.” National Cancer Institute. 1 May 2018. www.cancer.gov/about-cancer/treatment/types/radiation-therapy/external-beam. Accessed 16 Mar 2021.

“Getting Internal Radiation Therapy (Brachytherapy).” American Cancer Society. 10 Feb 2017. www.cancer.org/treatment/treatments-and-side-effects/treatment-types/radiation/internal-radiation-therapy-brachytherapy.html. Accessed 16 Mar 2021.

“Internal Radiation Therapy.” Canadian Cancer Society. www.cancer.ca/en/cancer-information/diagnosis-and-treatment/radiation-therapy/internal-radiation-therapy/?region=on. Accessed 16 Mar 2021.

“Understanding Radiation Therapy.” cancer.net. www.cancer.net/navigating-cancer-care/how-cancer-treated/radiation-therapy/understanding-radiation-therapy. Accessed 16 Mar 2021.