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.
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
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.
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.
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)
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 exam 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.
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 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.
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 another medical condition.
Generally, doctors will suggest a colonoscopy. A colonoscopy is slightly better at diagnosing cancer. Also, the doctor can do a biopsy (take a small sample of tissue to check for cancer) or remove any polyps during the colonoscopy.
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 bowels.
Preventing colon cancer
Certain lifestyle changes can reduce your risk of developing colon cancer.
- Maintain a healthy diet high in fiber, 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.
Dr. Prioty Islam is a Fellow in Hematology and Medical Oncology at Duke University Hospital in Durham, North Carolina. Prior to her position at Duke University, she completed an internship and residency in Internal Medicine at Emory University Hospital in Atlanta, GA, and is board-certified in Internal Medicine. She earned both her undergraduate degree and medical doctorate at the University of Pennsylvania in Philadelphia, PA. Dr. Islam is passionate about caring for patients with cancer, and has a wide breadth of expertise across cancer subtypes, with a particular interest in hematologic malignancies. She has helped design and conduct clinical trials to bring cutting edge therapeutics to her patients. Dr. Islam strongly values patient-centered care.