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Colon cancer: Everything you need to know

Colon cancer, also known as colorectal cancer, is the third most common type of cancer in men and women in the U.S., according to the Centers for Disease Control and Prevention (1). It’s more common in people over the age of 50 and more likely to affect those with a family history of colon polyps or polyps in other parts of the digestive tract, such as the small intestine (also known as adenomas).

What is Colon Cancer?

Colon cancer (2) is a disease in which cancer cells form in the tissues of the large intestine. The cancer forms in the innermost layer of the colon wall called the mucosa. The mucosa is made up of layers of cells that are constantly being shed and replaced. Through a process called apoptosis, these old cells are sloughed off and replaced with new ones.

Colon cancer occurs when these replacement cells develop mutations that allow them to grow and divide out of control. These abnormal cells may then spread to other parts of the body through the lymph system or bloodstream.

The most common type of colon cancer is called adenocarcinoma, which begins in the glandular tissue in the colon mucosa. The second most common type is called mucinous adenocarcinoma, which starts in glands that produce mucus, such as goblet cells. Mucinous adenocarcinomas tend to be less aggressive than other types of colon cancer because they grow more slowly and respond better to treatment.

Signs and Symptoms

Colon cancer is the third leading cause of cancer death in the U.S., after lung and prostate cancers.

The American Cancer Society (3) estimates that 142,000 new cases of colon cancer were diagnosed in 2016, and 50,000 people died from it. The incidence of colon cancer has been declining since the mid-1980s, but it remains one of the most common cancers in adults over 50 years old.

The five-year survival rate for those with localized disease (cancer confined to the colon) is more than 90%; however, this drops to only 20% if it has spread to lymph nodes or other organs at diagnosis.

Here are some signs and symptoms of colon cancer:

  • Bloody stool
  • A change in bowel habits that persists for 2 weeks or more (usually diarrhea or constipation (4))
  • Abdominal pain or cramping that lasts longer than 12 weeks
  • A feeling of not having completely emptied your bowels after a bowel movement
  • Loss of appetite or unintentional weight loss
  • Pelvic pain or rectal bleeding is not caused by hemorrhoids or irritation from wiping too hard or often
  • Fatigue (tiredness) and weakness

People usually have no symptoms at first, but some develop jaundice (yellowing of the skin caused by high levels of bilirubin).

Symptoms are usually caused by growths called polyps that develop along the lining of the colon. Polyps can become cancerous if they start to grow out through the wall of the colon or if they break off into another organ or nearby tissue. These growths are often benign (not cancerous) but sometimes turn into cancer over time.

According to the American Cancer Society (5), about 95 percent of all colon cancers begin as benign growths called polyps. Most of these are harmless and do not become malignant. However, some polyps can become malignant over time if they are not removed.

Colon cancer risk factors and statistics

  • About 96% of people diagnosed with colorectal cancer at the earliest stage will survive five years.
  • 1 in 125 men and 1 in 185 women will develop colorectal cancer during their lifetime.
  • The rate of colorectal cancer is higher among men than women. Men are also more likely to develop colon cancer before age 50 and rectal cancer before age 70. (6)
  • Colon cancer is four times more common than rectal cancer — about 73,000 new cases of colon cancer are expected in 2019 compared with 19,000 new cases of rectal cancer.
  • Colon cancer is more common among older people; it’s rare in young people under age 40.
  • African Americans and Hispanics have higher rates of colorectal cancer than whites and Asians do. Caucasians have higher rates than African Americans, Hispanics and Asians do. A few studies suggest that different ethnic groups may respond differently to some treatments for colorectal cancer, but more research is needed before doctors can recommend specific treatments based on race or ethnicity alone.
  • Having had a personal history of colorectal polyps (7) or colitis increases your risk of developing colon cancer by two to three times compared with someone who has not had them.
  • If you have a parent or sibling who had colon or rectal cancer before age 60, your risk increases by up to 6 times compared with those who don’t have a family history of these cancers. (8)
  • People who are overweight or obese are more likely to develop colorectal polyps than normal-weight people. (9)
  • Eating a diet high in red meat and low in fruits and vegetables may increase your risk of developing colon cancer, especially if you also have type 2 diabetes or metabolic syndrome (a group of conditions that includes diabetes). In addition, some research suggests that people who follow a vegetarian diet may have a lower risk of developing colon cancer than those who eat meat regularly.

Stages of Colon Cancer

Colon cancer stages (10)  are based on several factors, including the size of the tumor and whether it has spread (metastasized) to other tissues or organs. Your doctor will evaluate these factors and assign a stage to your colon cancer based on where it is in your body if it can be removed by surgery, if it’s spread to other parts of your body and how much time you have left before treatment is necessary for survival.

  • Stage 0: Cancer cells are only present in the inner lining of the colon (the mucosa). Stage 0 may also be called carcinoma in situ (CIS). Stage 0 colon cancer rarely spreads to other areas of the body.
  • Stage 1A: In stage 1A, there’s one small tumor in the mucosa and one or two smaller tumors in nearby lymph nodes. The cancer hasn’t spread outside these areas.
  • Stage 1B: In stage 1B, there’s one large tumor in the mucosa and one or two larger tumors in nearby lymph nodes. The cancer hasn’t spread outside these areas.
  • Stage 2: In stage 2, there are more than three tumors that have grown together into a mass in the wall of your colon. The cancer has also spread to nearby lymph nodes but not distant sites like muscle tissue or lungs.
  • Stage 3: In stage 3, multiple tumors have grown together into a larger mass in your colon wall and invaded tissues near your colon wall (like muscle). The cancer has also spread to distant sites like muscle tissue or lymf nodes (11).
  • Stage 4: colon cancer has spread from your colon to other parts of your body — most often to another organ such as your liver or lungs, or sometimes even to distant parts of your body like your bones or brain (metastasis).

Survival rates

Colon cancer is usually curable when it’s discovered in its early stages. But if it spreads to other parts of the body, it can be fatal.

The 5-year survival rate for colon cancer is about 65 percent, according to the National Cancer Institute (12). This means that after five years, about 65 out of 100 people still survive their disease. The 5-year survival rate estimates how many patients are likely to live at least five years after diagnosis if they receive treatment similar to that given to a specific group of patients who were studied (13).

The following factors may affect your prognosis:

  • The stage of your cancer: The earlier colon cancer is found and treated, the better your chances for recovery will be. The stage at which you are diagnosed is based on whether or not the cancer has spread from where it first began and whether there are lymph nodes involved (lymph nodes help fight infection). Stage II cancers have spread beyond the bowel wall into nearby tissue but have not spread to distant organs or lymph nodes. Stage III cancers have spread
  • The type of colon cancer: Your doctor can tell you what kind of colon cancer you have based on tissue samples (biopsy) from your tumor. Different types of cancer grow and behave differently. For example, adenocarcinoma tends to grow quickly, whereas neuroendocrine tumors tend to grow slowly over many years before they’re large enough to be seen on an X-ray exam or CT scan. Other types include adenosquamous carcinoma and other rare forms of the disease.
  • Where in your colon the cancer began: If you have a type of cancer called adenocarcinoma, which begins in mucus-producing glands and can start anywhere along the length of your colon, you’re more likely to survive than if you have other types of colon cancers, such as villous adenomas or tubular adenomas, which begin higher up in the colon and usually don’t spread beyond it until they become advanced stages of the disease.
  • The location of your tumor: If a tumor has invaded nearby tissues or organs, it can be harder to remove completely and could be more likely to recur. A tumor in the ascending colon (the part of the large intestine closest to your stomach) is less likely to recur than one in the descending colon or sigmoid colon (the part closest to your rectum).
  • Tumor markers: Tumor markers are substances released by tumors into the bloodstream that can be measured in blood tests. Some types of tumor markers can help doctors predict how fast tumors will grow and whether they will respond well to treatment.


The American Cancer Society (14) recommends that you begin screening for colon cancer at age 50 if you are at average risk of developing the disease. However, some people may be at higher risk and should start earlier. If you have a family history of colon cancer or polyps, or if there is a personal history of colorectal cancer in your family, talk to your doctor about whether you should begin screening sooner.

Screening for colon cancer involves tests that look for early signs of cancer in the colon and rectum. These tests include:

Fecal occult blood test (FOBT)

FOBT is an inexpensive, noninvasive method to detect colorectal cancer and other lower gastrointestinal diseases. It can be used in people with a family history of colorectal cancer or who have symptoms such as rectal bleeding, abdominal pain, or a change in bowel habits.

The FOBT test detects small amounts of blood in the stool that are not visible to the naked eye. These microscopic droplets of blood can indicate the presence of colon and rectal cancers, polyps, or inflammatory bowel disease.


A colonoscopy is a procedure that allows your doctor to examine the inside of your colon. Colonoscopies are used to detect and treat problems in the colon, such as polyps, ulcers, and cancerous tumors.

A colonoscopy is done in an outpatient center or hospital and takes about 30 minutes. It can be done as an outpatient procedure. You will be given anesthesia before the exam to make you sleep so that you don’t feel any discomfort during the exam.

During the exam, your doctor will insert a thin tube called a gastroscope inside you. The gastroscope has a light and camera attached to it so that your doctor can see inside your body on a television monitor while they move it through your intestine.

The doctor may also use other equipment such as biopsy forceps or resectoscopes to remove polyps from inside your colon during this procedure.

Blood stool test

A blood stool test is a rare type of stool test that analyzes the presence of red blood cells (RBCs). This test is often used to diagnose gastrointestinal bleeding, although it can also be used to evaluate other conditions such as colon cancer. It’s important to note that this test does not detect blood in the stool itself; rather, it detects the presence of RBCs in the digestive tract.

RBCs are typically found in stool samples because they sometimes pass through the intestines without being absorbed by the body. This can happen if there’s a tear in the intestine or if a person has an abnormally high number of RBCs in their bloodstream (polycythemia vera).

Stool immunochemistry

Stool immunochemistry is a blood test that looks for signs of infection in the stool. It can indicate when someone has diarrhea or other colon problems.

The stool immunochemistry test includes a sample of stool that is sent to a laboratory to be tested for certain chemicals and proteins. The chemicals tell doctors if there are harmful bacteria in the body, while the proteins can indicate if there’s a problem with digestion or absorption of nutrients.

Stool immunochemistry is used to detect the presence of bacteria, viruses, and parasites in the digestive system. It may also be used to detect inflammation or other problems with the digestive system. The results are usually available within one day of sending in your sample.

Barium enema X-ray

Barium enema X-rays are part of the diagnostic process for people who have lower gastrointestinal (GI) symptoms. They’re also used to evaluate conditions that affect the colon and rectum, such as cancer.

A barium enema X-ray involves placing a small amount of barium into your rectum (back passage) and colon using a tube called an enema bag. Barium is a contrast material that makes it easier for your doctor to see on an X-ray image.

You may get a barium enema X-ray if you have problems with constipation, diarrhea, or bowel obstruction. It’s also useful for checking for intestinal bleeding or inflammation — especially if you’re older than 60 years old and have any symptoms suggesting colon cancer, such as blood in your stool or unexplained weight loss.

How to prevent colon cancer?

Eating healthy is one of the best ways to prevent colon cancer. Fruits, vegetables, and whole grains provide fiber, which helps keep your digestive system moving smoothly. These foods also contain antioxidants that protect cells from damage caused by free radicals. Studies show that eating five servings of fruits and vegetables each day can help lower your risk of colon cancer by up to 20%.

Exercise is another important way to prevent colon cancer. Regular physical activity helps reduce stress levels and boosts immune function as well as strengthening muscles used during bowel movements. It also helps keep blood circulating throughout your body, which lowers your risk of developing blood clots that could lead to a life-threatening stroke or heart attack.

If possible, try to get in 30 minutes or more of moderate physical activity on most days of the week — such as walking briskly, biking, or swimming laps — or try an activity you enjoy like dancing or playing tennis with friends.

Smoking (15) is the most important risk factor for colon cancer. It causes about 20 percent of all cases in men and women combined. Smoking causes an estimated 90 percent of lung cancers but also increases the risk of developing other cancers, including those that start in the digestive tract, such as stomach and pancreatic cancers.

The molecular mechanisms by which smoking contributes to colorectal carcinogenesis are not completely understood.

It’s not just the smoking that may cause colon cancer. It’s also the toxic chemicals that are produced when alcohol is broken down by your body. These chemicals can damage DNA and cause mutations that lead to cancer.

Alcohol is a carcinogen, which means it can cause cancer in the body (16).  You may be wondering why you don’t see warning labels about alcohol being a carcinogen on every bottle of beer or glass of wine. The reason is that no proof drinking wine or beer causes cancer — only that drinking too much does (more than two drinks per day). In other words, if you’re going to drink, do so in moderation (no more than one drink per day for women and no more than two drinks per day for men).

Final thoughts

If you or a loved one is suffering from colon cancer, we hope these tips have given you some insight into the importance of early detection and ways to get the best possible treatment results. The most important thing to do if you’re suffering from colon cancer, or any colon disease, is to seek professional medical help.

Besides that, it’s important to stay motivated and know that there is hope for a successful recovery. Thankfully, there are many more treatment options available today than ever before!