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What types of radiation are there?

Radiation treatments can include:

  • External beam radiation therapy (EBRT)
  • Stereotactic body radiation therapy (SABR/SBRT/CyberKnife)
  • Proton therapy
  • Brachytherapy (Y90/SIRT)
  • Intraoperative radiation therapy
  • Intensity modulated radiation therapy (IMRT)
  • Brain stereotactic radiosurgery (Gamma Knife)
  • Palliative radiation therapy

Learn more about the different types below.

External beam radiation therapy (EBRT)

EBRT is the most commonly used type of radiation to treat rectal cancer. These radiation beams are very precise, targeting the tumor while avoiding as much of the surrounding healthy tissue as possible.

EBRT is usually given either as a long course — over 5 to 6 weeks — or as a short course, over just 5 days. Research has shown both types to be equally effective in many cases, although several factors can affect which type you may get. Your radiation oncologist will determine which is best for you.

Short course EBRT

Short course radiation therapy is usually given over 5 days. You will receive 5 gray (the unit we use to talk about radiation, often shortened to Gy) of radiation on each day — or 25Gy in total over 5 days.

Although this seems lower than the total radiation dose in long course EBRT, the radiation received by the tumor is comparable between the two regimens. Studies have shown the two approaches to be similarly effective in most circumstances.

Short course EBRT can reduce the total time spent in treatment and time off work for rectal cancer patients. 

However, short course radiation may result in more scarring of your rectum. Though recent studies show this not to be the case, many radiation oncologists hesistate to recommend it if you plan on following a non-operative, or “watch and wait” protocol. 

Short course radiation is the most common rectal cancer radiation treatment in many European countries.

Learn more about short course radiation therapy and non-operative rectal cancer management here:


Stage: IIIB

Type: Rectal cancer, with high rectal tumor

I received short-course radiation, which consisted of 5 treatments.

In general, my experience was very manageable. I didn’t have any issues with my skin or discomfort in my rectum. The only issue I had was back pain after my second treatment. It was very uncomfortable.

My doctor prescribed me a steroid pill that I took for two days. That took care of the pain, and it didn’t come back. I was given vaginal dilators, which I could use comfortably. There doesn’t appear to be any vaginal stenosis.

After my short course radiation I went through 6 rounds of CAPOX. My treatments worked well. I had a complete clinical response. I chose to not get the operation and am following a watch and wait protocol.

Long course EBRT

Long course radiation therapy is given over 25 to 28 days along with oral chemo tablets (capecitabine/Xeloda). You will receive 50Gy of radiation in total. 

Traditionally, long course EBRT has been the most common radiation therapy treatment plan, but recently, many centers have been moving in favor of the short course plan — especially due to the pandemic!

Long course radiation is preferred if you are planning to take a non-operative, or “watch and wait” approach. This is because long course radiation is thought to cause less scarring, so there’s less damage to the rectal tissue. Also, the current studies on the watch and wait approach have only been done with long course radiation, so we don’t have data to determine whether short course radiation works the same way. 

Want to learn more about long and short courst EBRT?

This article from Cancer Therapy Advisor discusses the advantages and disadvantages of the two approaches.

And this article from Memorial Sloan Kettering explains why short course radiation has recently gained more popularity in the US.

This DocTalk with Dr. VanderWalde gives an excellent overview of EBRT as rectal cancer treatment:


Stereotactic body radiation therapy (SABR/SBRT)

SBRT is a targeted radiation technique that is often used to treat small liver, lung, bone and brain metastases. This treatment is often called the CyberKnife, which refers to a brand of machine that is used.

It is more targeted than regular EBRT, so it allows the radiation oncologist to focus on a smaller area — sparing more of the healthy tissue. This is important in organs with more sensitive tissue, such as metastases in the brain.

This therapy is often used to target small tumors, where surgery is not a good option. This could be due to the location of the tumors, your overall health, or the presence of metastases in other organs.  There are usually a limited number of tumors that can be treated with SBRT — and the same area cannot usually be retreated if you have a local recurrence.

Proton therapy

This type of radiation uses proton beams instead of photon beams — the type used in standard EBRT. 

Proton beams may be able to target tumor tissue while sparing more healthy tissue.

Learn more about proton therapy in this DocTalk with Dr. Jethwa:


Brachytherapy radiation (Y90/SIRT)

This type of radiation is also called selective internal radiotherapy, or SIRT. It is usually used to treat inoperable liver metastases.

During treatment, tiny glass or resin beads — filled with the radioactive isotope yttrium Y90 — are placed inside the blood vessels that feed a tumor. 

Learn more about Y90 here:


Intraoperative radiation therapy

In this treatment, you’re given a high dose of radiation during surgery to kill any leftover cancer cells. This is done by an interventional radiologist in one large dose.

Intensity-modulated radiation therapy (IMRT)

IMRT is an advanced form of radiation therapy that delivers precise doses of radiation specifically to the tumor, or certain areas within the tumor. A highly sophisticated computer controls the radiation beams from different angles, allowing the radiologist to deliver higher doses of radiation to the tumor site, while minimizing damage to the surrounding healthy tissue.

Brain stereotactic radiosurgery

This is also called the Gamma Knife, referring to the brand of machine that is used. It is a non-invasive radiation treatment commonly used to treat brain metastases. This type of radiation is usually used when tumors are very small or located in places that are difficult to surgically remove.

Gamma Knife is an extremely precise form of radiotherapy that uses about 200 different beams from different angles to accurately deliver radiation to the tumor. 

Palliative radiation therapy

Radiation therapy can be used to relieve pain. If a tumor is pressing on a neighboring organ, and is causing pain or discomfort, radiation therapy can reduce the size of the tumor and provide relief. Speak to your healthcare team to discuss your options. 

Want to learn more about radiation?

Join one of our COLONTOWN Facebook groups:

  • In Rectalburgh, we discuss all things related to rectal cancer, including long and short course pelvic radiation
  • In Liver Lover’s Lane, we discuss liver metastases
  • Join us in Lungston for all things lung metastases
  • In Legoland, we talk bone metastases
  • Come join us in The Attic to learn more about brain metastases
  • If you want more information about distant lymph node metastases, join us in In the Distance
  • The Mighty Y-90 neighborhood has answers to all your questions about Y-90 treatment
  • Try Tough Chicks, a women’s only group, to chat about radiation side effects

Want to join? Fill out the registration form here.

COLONTOWN University has so much more to offer, from DocTalk videos with CRC experts to easy-to-understand biomarker test breakdowns. We’re here for you! See our list of Learning Centers here.

Last updated: April 28, 2022