Skip to main content
Read about

Colon Cancer

Learn how to prevent colon cancer, and how it’s treated.
Tooltip Icon.
Last updated May 13, 2024

Personalized colon cancer treatment

Get virtual care from a licensed clinician today

Get treated today

What is colon cancer?

Colon cancer, also called colorectal cancer, is a cancer of the large intestine (colon) and rectum. Most colon cancer starts with polyps that form on the colon lining. The American Cancer Society reports that colon cancer is the second leading cause of cancer deaths in the U.S.

Since colon cancer often doesn’t have any symptoms in its early stages, preventive screening is essential. It is recommended for men and women starting at the age of 45. (It was changed from age 50.) Screening may start at an even younger age for people with a higher risk of colorectal cancer due to family history (such as those with Lynch Syndrome).

Finding polyps and removing them is the best way to prevent colon cancer. One study published in the American Journal of Gastroenterology found that people who had a screening colonoscopy had an 89% reduced risk of colon cancer.

When colorectal cancer is found early—before it has spread to other parts of the body—the 5-year relative survival rate is about 90%. But according to the American Cancer Society, only about 40% of colorectal cancers are found at this early stage. When cancerous cells have spread outside the colon or rectum, survival rates are lower.

Most common symptoms

Pro Tip

People think colon cancer is always a terminal illness. The truth is, there are many treatments for colon cancer. If treated early, colon cancer can even be cured. —Dr. Prioty Islam

Both noncancerous and cancerous polyps don’t usually cause symptoms. Even after polyps become cancer, symptoms are unlikely until the growth is large.

At that point, the growth may block the large intestine or bleed into the stools. The cancer may also have gone into the wall of the intestine and spread to nearby lymph nodes in the abdomen or to other organs.

Main symptoms

Most early-stage colon cancer is asymptomatic (without symptoms). When there are symptoms, these are some of the most common:

Screening for colon cancer

Talk to your doctor about risk factors to see if you need to start screenings earlier than at age 45. Also, ask about which screening test is right for you. Depending on your own risk of colon cancer, your doctor may recommend one screening test over another.

Stool tests

There are a few different kinds of stool tests. They all involve testing stool for hidden (occult) blood. The tests can usually be done at home, though sometimes the sample is sent to a lab. They include:

  • Fecal occult blood test (FOBT)
  • Fecal immunochemical test (FIT)
  • Fecal immunochemical test with DNA testing (FIT-DNA)

Visual tests

There are a few medical tests that allow a doctor to check your colon for signs of cancer, like polyps, or other issues.

The most common test is the colonoscopy, which allows the doctor to examine the entire colon. A sigmoidoscopy is less invasive, but the doctor can only view the rectum and the lower part of the colon. If the doctor sees anything unusual during a sigmoidoscopy, then you might need a colonoscopy, too. In both tests, the doctor can remove any polyps they see, which prevents them from developing into cancer.

  • For either test, you will do a colon prep, which means clearing out your colon so the doctor can see the walls of the colon and rectum. You’ll be given a cleansing drink with directions on how to use it.
  • Immediately before a colonoscopy, you are given a sedative. A sedative is often not needed for a sigmoidoscopy. But your doctor may give you medicine to help you relax.
  • During both procedures, you will lie down on your side with your knees bent. The doctor will gently insert a lubricated, flexible, lighted tube (an endoscope) through the anus into the rectum. Air is pumped into the bowel so the tube can be positioned properly.

A colonoscopy is recommended every 10 years. A sigmoidoscopy is recommended every 5 years. But either could be more often, depending on findings during the procedure.

Another test is a CT (computed tomography) colonography. It uses a CT scanner (X-rays) to check the colon for any abnormalities. Screening is recommended every 5 years.


Pro Tip

An important question to ask your doctor is: What stage is the cancer? —Dr. Islam

Most colon cancers start from polyps that grow in the colon. Only a small percentage (about 1%) of polyps in the colon become cancerous.

A polyp usually grows slowly. It takes 5 to 10 years for it to become cancer. So if you have a polyp removed before it becomes malignant (cancer), it can’t develop into colon cancer.

Colon cancer is believed to have some connection to lifestyle habits such as obesity, a high-fat, low-fiber diet, and smoking cigarettes. Heredity also plays a role. Up to 25% of people with colon cancer have family members who have had the disease.

It is also more common in certain racial and ethnic groups.

  • Black people have the highest colorectal cancer and mortality (death) rates of all racial groups in the U.S. The reasons for this are not fully understood, but it may be a combination of genetics and access to health care.
  • Jews of Eastern European descent (Ashkenazi Jews) have one of the highest colorectal cancer risks of any ethnic group in the world.

Several diseases increase the chance of colon cancer including inflammatory bowel disease (especially ulcerative colitis) and possibly diabetes.

Next steps

If you have rectal bleeding, your doctor may want to do one or more tests. When you have bright red blood, sigmoidoscopy is often the first approach since bleeding is usually from the far end of the colon.

If a screening test for hidden blood is positive, your doctor will want to try to figure out where the blood is coming from. Your doctor will probably want to do either a barium enema (an X-ray of the colon) or a colonoscopy. Both procedures can help diagnose colon cancer or other medical condition.

Generally, doctors will suggest a colonoscopy. A colonoscopy is slightly better at diagnosing cancer syndrome. Also, the doctor can do a biopsy (take a small sample of tissue to check for cancer) or remove any polyps during the colonoscopy.

Dr. Rx

See a doctor as soon as something seems off. Many people are nervous, anxious, or scared when they’re thinking about getting help for a possible diagnosis of colon cancer. It is vital to seek help and not ignore or brush off symptoms. —Dr. Islam


Colon cancer has many different stages. Stage 0 is very early cancer. Stage IV is the most advanced stage. It means the cancer has spread to two or more areas.

Your treatment options are determined by which stage it is. Surgery to remove all or part of the bowel is recommended for every stage. The procedure is called a colectomy.

The surgery can also be done using an endoscope after the surgeon makes several keyhole incisions in the abdomen.

Sometimes, after surgery, you will need radiation therapy, chemotherapy, or both. If your doctor, does not have to remove the anal sphincter, then you should still be able to control your bowel habits.

Ready to treat your colon cancer?

We show you only the best treatments for your condition and symptoms—all vetted by our medical team. And when you’re not sure what’s wrong, Buoy can guide you in the right direction.See all treatment options
Illustration of two people discussing treatment.

Preventing colon cancer

Certain lifestyle changes can reduce your risk of developing colon cancer.

  • Maintain a healthy diet high in fiber, and low in fat, with several daily servings of fruit and vegetables, especially leafy greens.
  • Stay active by exercising, and also maintain a healthy body weight. It can protect you against colon cancer along with many other types of cancers.
  • Don’t smoke or vape.
  • Drink alcohol moderately. The CDC guidelines recommend no more than one drink per day for women and no more than two for men.
  • Get regular screenings. Follow your doctor’s guidance for how often to have colon cancer screenings.
Illustration of a healthcare provider asking questions on a smart phone.
Virtual weight loss solution
A personalized GLP-1 medication program (eg. Wegovy, Ozempic) delivered to you via our partner Korb Health
Illustration of a healthcare provider asking questions on a smart phone.
  • Free consultation; program starts at $269/mo
  • Checkmark Inside Circle.Customized online program and wellness coaching
  • Prescription medications and supplies shipped to your door
Get treatment today
Share your story
Once your story receives approval from our editors, it will exist on Buoy as a helpful resource for others who may experience something similar.
The stories shared below are not written by Buoy employees. Buoy does not endorse any of the information in these stories. Whenever you have questions or concerns about a medical condition, you should always contact your doctor or a healthcare provider.
Dr. Le obtained his MD from Harvard Medical School and his BA from Harvard College. Before Buoy, his research focused on glioblastoma, a deadly form of brain cancer. Outside of work, Dr. Le enjoys cooking and struggling to run up-and-down the floor in an adult basketball league.

Was this article helpful?

9 people found this helpful
Tooltip Icon.
Read this next
Slide 1 of 4