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Colorectal Cancer after Childhood Cancer Treatment

Some childhood cancer treatments may increase the risk of developing colorectal cancer.

What is colorectal cancer?

Colorectal cancer is cancer that happens in the colon and/or the rectum. The colon is the longest part of the large intestine. The rectum is the last several inches of the large intestine.

Risk factors for colorectal cancer in childhood cancer survivors

Risk increases for patients who had radiation to the:

  • Belly
  • Spine
  • Pelvis
  • Total body

Total body radiation is sometimes used to prepare patients for a stem cell (bone marrow) transplant.

Most people who had radiation to the belly, spine, and pelvis will not develop colorectal cancer as a result of treatment. But the risk is higher than it is for people who have never had radiation.

Colorectal cancer in childhood cancer survivors medical illustration

Most colorectal cancers start as a polyp, a small, harmless growth. A colonoscopy can find these polyps, so they can be removed before they develop into cancer.

Symptoms of colorectal cancer

During the early stages of colorectal cancer, there are rarely signs and symptoms.

Most colorectal cancers begin as a polyp. A polyp starts as a small, harmless growth in the wall of the colon or rectum. As the polyp gets larger, it can develop into cancer.

A colonoscopy can find polyps. They can be removed during the procedure.

Signs and symptoms appear as cancer advances. If you have any of these symptoms, contact a health care provider right away:

  • Bleeding from the rectum
  • Blood in the stool or in the toilet after a bowel movement
  • A change in the shape of the stool
  • Cramping pain in the lower stomach
  • Discomfort or an urge to have a bowel movement when there is no need to have one
  • A change in the normal frequency of bowel movements

Other conditions may cause these signs and symptoms. Your health care provider can evaluate them to find out what may cause them.

The risk for colorectal cancer starts to increase about 10 years after radiation.

In the general population, colorectal cancer is most likely to occur between ages of 45–65. Cancer may occur earlier in childhood cancer survivors who had radiation to areas near the colon and rectum.

Other risk factors

Other risk factors that could lead to colorectal cancer include:

  • Previous colorectal cancer or large polyps in the intestine
  • A close relative who had colorectal cancer before age 60
  • Ulcerative colitis or Crohn disease
  • Hereditary colon cancer syndromes, such as familial adenomatous polyposis

What survivors can do

Questions to ask about colorectal cancer

When you talk to your health care provider, here are some questions you can ask:

  • What screenings do you suggest?
  • At what age should I begin screenings?
  • How often should I have screenings?
  • What is my risk of developing colorectal cancer?
  • What can I do to prevent getting colorectal cancer?

Key points about colorectal cancer

  • Colorectal cancer is cancer that happens in the colon and/or the rectum.
  • Colorectal cancer does not have symptoms in the early stages. It usually begins as polyps. These small growths can be found and removed during a colonoscopy.
  • Radiation to the belly, spine, or pelvis can increase the risk of colorectal cancer.
  • Childhood cancer survivors who had radiation therapy to the belly, spine, or pelvis should start getting colorectal screenings 5 years after radiation or at age 30, whichever is later.
  • Eating healthy foods and being physically active may reduce the risk of colorectal cancer.

Reviewed: October 2023