Colorectal Cancer

Colorectal cancer is a cancerous (malignant) tumor in the colon or rectum, which are parts of the large intestine. A tumor is a mass of cells or tissue. The cancer can spread (metastasize) to other parts of the body.

What are the causes?

This condition is usually caused by abnormal growths called polyps on the inner wall of the colon or rectum. Left untreated, these polyps can develop into cancer. Other times, abnormal changes to genes (gene mutations) can cause cells to become cancerous.

What increases the risk?

The following factors may make you more likely to develop this condition:

Being older than age 50.
Having a personal or family history of colorectal cancer or polyps in your colon.
Having diabetes, or having had cancer and cancer treatments such as radiation before.
Having certain hereditary conditions, such as:
- Lynch syndrome.
- Familial adenomatous polyposis.
- Turcot syndrome.
- Peutz–Jeghers syndrome.
- MUTYH-associated polyposis (MAP).
Being overweight or obese.
Having a diet that is:
- High in red meats, such as beef, pork, lamb, or liver.
- High in precooked, cured, or other processed meat, such as sausages, meat loaves, and hot dogs.
- Low in fiber, such as fiber found in whole grains, fruits, and vegetables.
Being inactive (sedentary), smoking, or drinking too much alcohol.
Having an inflammatory bowel disease, such as ulcerative colitis or Crohn's disease.

What are the signs or symptoms?

Early colorectal cancer often does not cause symptoms. As the cancer grows, symptoms may include:

Changes in bowel habits.
Feeling like the bowel does not empty completely after a bowel movement.
Stools (feces) that are narrower than usual, or blood in the stool or toilet after a bowel movement. The blood may be bright red or very dark in color.
Diarrhea, constipation, or frequent gas pain.
Anemia, constant tiredness (fatigue), or nausea and vomiting.
Discomfort, pain, bloating, fullness, or cramps in the abdomen.
Unexplained weight loss.

How is this diagnosed?

This condition may be diagnosed with:

A medical history.
A physical exam.
Tests. These may include:
- An exam of the rectum using a gloved finger (digital rectal exam).
- A stool test called a fecal occult blood test.
- Blood tests.
- A biopsy. This is removal of a tissue sample from the colon or rectum to be looked at under a microscope.

You may also have other tests, including:

X-rays, CT scans, MRIs, or a PET scan.
A sigmoidoscopy. This test is done to view the inside of the rectum.
A colonoscopy. This test is done to view the inside of the colon. During this test, small polyps can be removed or biopsies may be taken.
An endorectal ultrasound. This test checks how deep a tumor in the rectum has grown and whether the cancer has spread to lymph nodes or other nearby tissues.

Additional tests may be done to find out whether the cancer has spread to other parts of the body (what stage it is). The stages of cancer include:

Stage 0 – At this stage, the cancer is found only in the innermost lining of the colon or rectum. The tumor has not spread to other tissue.
Stage 1 (I) – At this stage, the cancer has grown into the inner wall (muscle layer) of the colon or rectum.
Stage 2 (II) – At this stage, the cancer has grown more deeply into the wall of the colon or rectum or through the wall. It may have invaded nearby tissue or organs.
Stage 3 (III) – At this stage, the cancer has spread to nearby lymph nodes or tissue near the lymph nodes.
Stage 4 (IV) – At this stage, the cancer has spread to other parts of the body that are not near the colon, such as the liver or lungs.

How is this treated?

Treatment for this condition depends on the type and stage of the cancer. Treatment may include:

Surgery. In the early stages of the cancer, surgery may be done to remove polyps or small tumors from the colon. In later stages, surgery may be done to remove part of the colon (partial colectomy).
Chemotherapy. This treatment uses medicines to kill cancer cells.
Targeted therapy. This treatment can kill tumor cells by targeting specific gene mutations or proteins that the cancer expresses.
Immunotherapy (biologic therapy). This treatment uses your body's disease-fighting system (immune system) to fight the cancer. Substances made by your body or in a laboratory are used to boost, direct, or restore your body's natural defenses against cancer.
Radiation therapy. This treatment uses radiation to kill cancer cells or shrink tumors.
Radiofrequency ablation. This treatment uses radio waves to destroy the tumors that may have spread to other areas of the body, such as the liver.

Follow these instructions at home:

Take over-the-counter and prescription medicines only as told by your health care provider.
Try to eat regular, healthy meals. Some of your treatments might affect your appetite. Ask to meet with a dietitian if you are having problems eating or with your appetite.
Consider joining a support group. This may help you learn about your diagnosis and manage the stress of having colorectal cancer.
If you are admitted to the hospital, tell your cancer care team.
Keep all follow-up visits. This is important.

How is this prevented?

Colorectal cancer can be prevented with screening tests that find polyps so they can be removed before they develop into cancer.
All adults should have screening for colorectal cancer starting at age 45 and continuing until age 75. Your health care provider may recommend screening before age 45. People at increased risk should start screening at an earlier age.
You may be able to help reduce your risk of developing colorectal cancer by staying at a healthy weight, eating a healthy diet, avoiding tobacco and alcohol use, and being physically active.

Where to find more information

American Cancer Society: cancer.org
National Cancer Institute (NCI): cancer.gov

Contact a health care provider if:

Your diarrhea or constipation does not go away.
You have blood in your stool or in the toilet after a bowel movement.
Your bowel habits change.
You have increased pain in your abdomen.
You notice new fatigue or weakness.
You lose weight without a known reason.

Get help right away if:

You have increased bleeding from the rectum.
You have any uncontrollable or severe abdominal symptoms.

Summary

Colorectal cancer is a cancerous (malignant) tumor in the colon or rectum, which are parts of the large intestine.
Common risk factors for this condition include being older than age 50, having a personal or family history of colorectal cancer or colon polyps, having certain hereditary conditions, or having conditions such as diabetes or inflammatory bowel disease.
This condition may be diagnosed with tests, such as a colonoscopy and biopsy.
Treatment depends on the type and stage of the cancer. Often, treatment includes surgery to remove the abnormal tissue, along with chemotherapy, targeted therapy, or immunotherapy.
Keep all follow-up visits. This is important.