When is Radiation Therapy Right for Me?

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Radiation therapy treats cancer by using high doses of radiation to kill cancer cells and shrink tumors. These high-energy rays are targeted toward the location of tumors in an effort to localize its effects. Though radiation is rarely used to treat colorectal cancer by itself, it is sometimes used simultaneously with chemotherapy. When radiation and chemotherapy are used in conjunction with each other, this is typically called chemoradiation or chemoradiotherapy.

Radiation works by killing cancer cells by damaging their DNA, rendering them unable to continue dividing indefinitely. Once these damaged cancer cells die, the immune system can then break down the cells.

When radiation is used in the treatment of colorectal cancer, it is typically used in conjunction with other treatment methods. When used with surgery, radiation therapy is typically used to shrink tumors to make them easier to remove, or to kill lingering cancer cells during or after surgery. Radiation is used alongside chemotherapy when a patient isn’t healthy enough for surgery, to treat cancer that has spread to other areas of the body, or palliatively,  to ease symptoms of advanced stage cancer.

Radiation Therapy for Colon Cancer 

Radiation therapy is not often used to treat colon cancer unless it is in the treatment of tumors that have grown next to or into other organs, to improve your quality of life, or to improve outcomes of surgery. Uses of radiation therapy to treat colon cancer include:

  • Shrink tumors before surgery to make it easier to remove
  • Intraoperative Radiation Therapy (IORT): Kill lingering cancer cells during surgery
  • Kill lingering cancer cells after surgery
  • Treat a person who is not healthy enough for surgery, along with chemo
  • Treat cancer that has metastasized to other areas of the body
  • Improve the quality of life of patients with advanced stage cancer causing intestinal blockages, bleeding, or pain

Radiation Therapy for Rectal Cancer 

Radiation therapy is more often used to treat rectal cancer in comparison to colon cancer, and it is used in similar ways – to treat tumors that have grown next to or into other organs, to improve your quality of life, or to improve outcomes of surgery. Uses of radiation therapy to treat rectal cancer include:

  • Shrink tumors before surgery to make it easier to remove, especially if tumors are located in an area that is difficult to operate
  • Intraoperative Radiation Therapy (IORT): Kill lingering cancer cells during surgery
  • Kill lingering cancer cells after surgery
  • Treat a person who is not healthy enough for surgery, along with chemo
  • Treat cancer that has metastasized to other areas of the body
  • To treat recurring tumors in the pelvis after radiation has been used
  • Improve the quality of life of patients with advanced stage cancer causing intestinal blockages, bleeding, or pain

Learn more about radiation treatment for colon and rectal cancer in this CRC Webinar with Dr. Michael Bassetti from the UW School of Medicine and Public Health. We review why radiation therapy is used, how to prepare for treatment, how to manage side effects and more.

Advantages & Disadvantages of Radiation Therapy

Advantages

  • Decreases the chance of tumor recurrence in the pelvis or near the rectum and adjacent lymph nodes by 50%
  • Decreases the chance of an operation causing permanent colostomy
  • Less toxicity from chemoradiation if done prior to surgery
  • Effective, non-invasive, and well-tolerated for treating metastatic colorectal cancer

Disadvantages

  • Can cause new mutations to be created or new antigens to be expressed
  • Dying tumor cells release antigens and pro-inflammatory cytokines
  • Removes immunosuppressive immune cells
  • Inconvenience (e.g. in some cases radiation must be delivered daily)
  • Can cause poor wound healing if surgery is performed after radiation therapy

Types of Radiation Therapy

The two main types of radiation therapy are defined by the method that radiation is delivered – externally or internally. External-beam radiation therapy is delivered by a machine aimed at the location of your tumor. Internal radiation therapy is delivered by a radiation source that is put inside the body in solid or liquid form.

External-beam Radiation Therapy (EBRT)

  • Machine emits radiation targeted at the location of a tumor
  • Local treatment: Only treats the area the radiation is delivered to
  • Treatments given over the course of a few days to several weeks

Internal Radiation Therapy

Endocavitary Radiation Therapy

  • Solid source of radiation are placed in the body in or near a tumor
  • In treating rectal cancer, a small balloon-like device is placed in the rectum to deliver radiation for a few minutes
  • Local treatment
  • Treatments typically given 4 times or less, with 2 weeks between each treatment

Interstitial Brachytherapy

  • Solid source of radiation are placed in the body in or near a tumor
  • In treating rectal cancer, tube is placed into the rectum and into the tumor to deliver radiation pellets for a few minutes
  • Local treatment
  • Treatments given a few times a week for several weeks, or can be a one-time procedure

What to Expect from Radiation Therapy

Your ability to carry on normal activities depends on the type of radiation therapy being administered and its frequency. Depending on the schedule of your radiation therapy, you may be required to stay at the hospital. Some patients may be able to perform normal daily activities, like working full-time or part-time, without much interruption, while others may be too fatigued. Side effects from radiation therapy typically go away after treatment in a few weeks or a few months.

Over the course of your lifetime, there is a limit to the amount of radiation you can be exposed to. If you have had radiation therapy in the past, you may not be eligible to receive radiation to the same area of your body if you’ve reached your safe lifetime dose of radiation. However, if you have already reached your lifetime limit in one are of your body, you may be eligible to receive radiation therapy again targeted toward another area.

Radiation Therapy Side Effects

Radiation only affects the area of the body where it is administered (except in the case of systemic radiation therapy). Thus, radiation therapy for colorectal cancer should not cause hair loss, unless radiation is administered to the scalp. However, when given locally, radiation can also damage or kill nearby healthy cells that can cause negative side effects. Most side effects disappear after treatment

  • Skin irritation at the site of radiation exposure (redness, blistering, or peeling)
  • Nausea
  • Fatigue
  • Hindered wound healing if administered before surgery
  • Rectal irritation (diarrhea, painful bowel movements, or blood in the stool)
  • Bowel incontinence
  • Bladder irritation (frequent urination, burning or pain, blood in the urine)
  • Sexual problems (such as erectile dysfunction or vaginal irritation)
  • Changes in menstruation
  • Infertility
  • Scarring or fibrosis that cause tissues to stick together

More Treatment Resources

Radiation therapy is only used to treat colon and rectal tumors under certain circumstances, and usually used in conjunction with other colorectal cancer treatments. Find out more about colorectal cancer chemotherapy and colorectal cancer surgery