Colon Cancer

Colon cancer is a growth of cells that begins in a part of the large intestine called the colon, and while it typically affects older adults, it can happen at any age. Thanks to screening tests that detect and remove precancerous polyps, early treatment, and new kinds of treatment, fewer people are dying from this disease.

Table of contents

• What Is Colon Cancer?
• Associated Anatomy
• Who Is Affected by Colon Cancer
• Signs and Symptoms
• Diagnosis
• Stages of Colon Cancer
• Treatment Options
• Prevention and Risk Reduction
• Screening and Early Detection
• Living with and After Colon Cancer

colorectal cancer, colon carcinoma

What Is Colon Cancer?

Colon cancer is a growth of cells that begins in a part of the large intestine called the colon. The colon is the first and longest part of the large intestine, which is the last part of the digestive system. The digestive system breaks down food for the body to use^[1].

Colon cancer starts in the innermost lining of the colon, called the mucosa (the layer of tissue that lines organs and produces mucus and other fluids). It consists of cells that make and release mucus and other fluids. If these cells change or mutate (undergo changes in their genetic material), they may create a colon polyp (a small clump of cells that forms on the lining of the colon)^[2].

Colon cancer typically begins as small clumps of cells called polyps that form inside the colon. Polyps generally aren’t cancerous, but some can turn into colon cancers over time. It usually takes about 10 years for cancer to form in a colon polyp^[1][2].

Over time, colon polyps may become cancerous. Left undetected or untreated, the cancer works its way through a layer of tissue, muscle, and the outer layer of the colon. The colon cancer may also spread to other parts of the body via lymph nodes or blood vessels^[2].

Associated Anatomy

• Colon (large intestine)
• Rectum
• Small intestine
• Digestive system
• Lymph nodes
• Blood vessels

The colon is part of the body’s digestive system. The digestive system takes in nutrients such as vitamins, minerals, carbohydrates, fats, proteins, and water from foods and helps pass waste material out of the body. The digestive system is made up of the esophagus, stomach, and the small and large intestines. The colon (large bowel) is the main part of the large intestine and is about 5 feet long^[13].

The colon can be divided into the right colon (cecum, ascending colon, and right two-thirds of the transverse colon) and left colon (left one-third of the transverse colon, descending colon, and sigmoid colon). The blood supply of the colon is mainly from the mesenteric artery. The function of the right colon is mainly to absorb water and some nutrients, while the main function of the left colon is to store and excrete waste^[4].

Who Is Affected by Colon Cancer

Colon cancer is the third most common cancer diagnosed in people in the United States. According to the U.S. Centers for Disease Control and Prevention, males are slightly more likely to develop colon cancer than females. Colon cancer affects more people who are Black than people who are members of other ethnic groups or races^[2].

Colon cancer typically affects people age 50 and older. Over the past 15 years, however, the number of people age 20 to 49 with colon cancer has increased by about 1.5% each year. Medical researchers aren’t sure why this is happening^[2].

Colon cancer is the third most common cancer worldwide, accounting for approximately 10% of all cancer cases and is the second leading cause of cancer-related deaths worldwide. It predominantly affects older individuals, with the majority of cases occurring in people aged 50 and above^[9].

More than 50,000 Americans die from colon cancer each year—that’s nearly 140 people a day. The lifetime risk of developing colon cancer is 4 to 5% in men and women, though men may get colon cancer at an earlier age than women^[6].

Signs and Symptoms

Many people with colon cancer don’t have symptoms at first. When symptoms appear, they’ll likely depend on the cancer’s size and where it is in the colon^[1]. You can have colon cancer without having symptoms. If you do have symptoms, you may not be sure if changes in your body are signs of colon cancer because some colon cancer symptoms are similar to symptoms of less serious conditions^[2].

Common symptoms of colon cancer include^[2][7]:

• Blood on or in your stool: You might notice blood in the toilet after you poop or after wiping, or your poop may look dark or bright red. It’s important to remember blood in poop doesn’t mean you have colon cancer. Other things—from hemorrhoids to anal tears to eating beets—may change your poop’s appearance. But it’s always better to check with a healthcare provider any time you notice blood in or on your stool. The blood can be bright red, or the stool may be black and tarry or brick red.
• Persistent changes in your bowel habits: Talk to a healthcare provider if you have persistent constipation or diarrhea, or if you feel as if you still need to poop after going to the bathroom. This may include intermittent or constant diarrhea or constipation, a change in the consistency of your stool, or stools that are more narrow than usual.
• Abdominal (belly) pain: Talk to a healthcare provider if you have belly pain with no known cause, that doesn’t go away or hurts a lot. Many things may cause belly pain, but it’s always best to check with a healthcare provider if you have unusual or frequent belly pain.
• Bloated stomach: Like belly pain, there are many things that may make you feel bloated. Talk to a healthcare provider if your bloated belly lasts for more than a week, gets worse, or you have other symptoms.
• Unexplained weight loss: Losing weight without trying can be a symptom.
• Fatigue and weakness: Feeling unusually tired or weak can occur.

People with colon cancer may experience subtle signs and symptoms including fatigue, weakness, weight loss, abdominal pain, changes in bowel habit, and rectal bleeding. However, many people will have no symptoms at all, especially during the early stages. This is why screening for colon cancer is extremely important^[6].

Diagnosis

Tests and procedures used for colon cancer diagnosis include^[10]:

Using a scope to examine the inside of the colon: Colonoscopy (an exam using a long, flexible tube with a camera attached) uses a long, flexible and slender tube attached to a video camera and monitor to view the whole colon and rectum. A doctor may pass surgical tools through the tube to take tissue samples and remove polyps^[10].

Removing a sample of tissue for testing: A biopsy (a procedure to remove a sample of tissue for testing in a lab) is a procedure to remove a sample of tissue for testing in a lab. For colon cancer, the tissue sample is often collected during a colonoscopy. Sometimes surgery is needed to get the tissue sample. In the lab, tests can show whether the cells are cancerous and how quickly they’re growing. Other tests can give more information about the cancer cells. Your health care team uses the results to understand your prognosis and create a treatment plan^[10].

Blood tests: Blood tests aren’t used to diagnose colon cancer. But blood tests can give clues about overall health, such as how well the kidneys and liver are working. A blood test might be used to look for a low level of red blood cells. This result might indicate that a colon cancer is causing bleeding. Colon cancers sometimes make a protein called carcinoembryonic antigen, also called CEA. Blood tests can track the level of CEA over time. The results might show whether the cancer is responding to treatment. After treatment, CEA blood tests might detect if the cancer comes back^[10].

Stages of Colon Cancer

After colon cancer has been diagnosed, imaging tests are done to find out if cancer cells have spread within the colon or to other parts of the body^[13]. The stages of colon cancer help doctors understand how far the disease has progressed and guide treatment decisions^[10].

The 5-year survival rate after detection and treatment of early-stage colon cancer can be as high as 90%. Unfortunately, the 5-year survival rate after treatment of late-stage colon cancer is much lower^[6].

The prognosis for colorectal cancer varies depending on the stage at diagnosis. Early-stage cancers have higher survival rates than advanced-stage cancers. Timely diagnosis, appropriate treatment, and regular follow-up care are important for improving survival rates and quality of life^[9].

Treatment Options

If colon cancer develops, many treatments can help control it. Treatments include surgery, radiation therapy and medicines, such as chemotherapy, targeted therapy and immunotherapy^[1].

Multiple treatment modalities, depending on the stage of the tumor and patient characteristics, are available. These include surgery, chemotherapy, radiotherapy, molecular targeted therapy, immunotherapy, and other programs^[4].

Surgery: Surgery is commonly used to treat colon cancer. For early-stage colon cancer, surgery may involve removing polyps or small sections of the colon. For more advanced cancer, larger portions of the colon may need to be removed. Some people may need a colostomy (a surgical opening in the abdomen through which waste can pass) or ileostomy (a similar opening using the small intestine)^[15].

Chemotherapy: Chemotherapy is commonly used to treat colorectal cancer. It uses drugs to kill cancer cells or stop them from growing^[15].

Radiation therapy: Radiation therapy is most often used to treat rectal cancer, though it can be used for colon cancer in some cases^[15].

Targeted therapy: Targeted therapy is used to treat advanced colorectal cancer. It works by targeting specific molecules involved in cancer growth^[15].

Immunotherapy: Metastatic colorectal cancer is sometimes treated with immunotherapy. It helps strengthen the immune system to fight cancer^[15].

Prevention and Risk Reduction

The risk of colorectal cancer can be reduced by eating a healthy diet, staying physically active, not smoking tobacco and limiting alcohol^[9].

Several lifestyle factors contribute to the development of colorectal cancer such as a high intake of processed meats and low intake of fruits and vegetables, sedentary lifestyle, obesity, smoking, and excessive alcohol consumption^[9].

In addition to colorectal cancer screening, doctors recommend making simple lifestyle changes to help reduce your risk of developing colorectal cancer^[20]:

• Stop smoking: Smoking may increase colorectal cancer risk. Doctors strongly urge people who smoke to quit.
• Limit alcohol intake: Heavy alcohol use may increase the risk of developing colon cancer. Doctors advise drinking alcohol in moderation only.
• Eat a healthy diet: Eating a healthy diet—one rich in fruits, vegetables, and whole grains and low in red and processed meats—may help reduce your risk of developing colorectal cancer. A high intake of red and processed meats has been shown to increase the risk of colorectal cancer.
• Exercise regularly: An active lifestyle has been linked to a reduced risk of colorectal cancer. Speak with your doctor about an exercise program that is right for you.
• Maintain a healthy weight: Being overweight can increase your risk of colorectal cancer. Eating healthfully and exercising regularly can help you maintain a healthy body weight.

Screening and Early Detection

Colorectal cancer is one of the most preventable types of cancer. Most colon cancers develop from small growths in the lining of the colon and rectum, called polyps. Certain types of polyps grow over time and transform into cancer. Finding and removing these “pre-cancerous” polyps can prevent this type of cancer^[6].

Polyps often don’t cause symptoms. For this reason, doctors recommend regular screening tests to look for polyps in the colon. Finding and removing polyps helps prevent colon cancer^[1].

Healthcare providers have screening tests that detect precancerous polyps before they can become cancerous tumors. Colon cancer that’s not detected or treated may spread to other areas of the body. Thanks to screening tests, early treatment and new kinds of treatment, fewer people are dying from colon cancer^[2].

People at average risk should have a screening colonoscopy as early as age 45. Colorectal cancer rates have been increasing in people under the age of 50. Due to this trend, the recommended age to begin screening colonoscopy was lowered from age 50 to 45 for average risk individuals. The rates have even been increasing in young people, including those in their 20s and 30s^[6].

Those at higher risk of colon cancer include people with a family history of colon cancer, inherited colorectal cancer syndrome, or a known predisposing gastrointestinal disorder. If you think you may be at increased risk for colorectal cancer, speak with your doctor about when to begin screening, which test is right for you, and how often to get tested^[5][6].

Colonoscopy is the most effective colorectal cancer screening test. There are several types of colorectal screening and detection tests, such as stool testing, radiological imaging (virtual colonoscopy), and flexible sigmoidoscopy. However, colonoscopy is the only test in which the entire colon can be visualized using a colonoscope and pre-cancerous polyps can be removed. Cancer risk is reduced by 90% after colonoscopy and polyp removal, according to estimates. Cancer incidence has dropped by 30% after the widespread uptake in screening colonoscopy^[6].

Colorectal cancer screening saves lives. Early detection of colon cancer through screening can save a person’s life^[6].

Risk factors for colorectal cancer include^[13]:

• Having a first-degree relative (parent, sibling, or child) with a history of colon or rectal cancer
• Having a personal history of colon, rectal, or ovarian cancer
• Having a personal history of high-risk adenomas (colorectal polyps that are 1 centimeter or larger in size or that have cells that look abnormal under a microscope)
• Having inherited changes in certain genes that increase the risk of familial adenomatous polyposis or Lynch syndrome (hereditary nonpolyposis colorectal cancer)
• Having a personal history of chronic ulcerative colitis or Crohn disease for 8 years or more
• Having three or more alcoholic drinks per day
• Smoking cigarettes
• Being Black
• Having obesity
• Older age is a main risk factor for most cancers. The chance of getting cancer increases as you get older.

Living with and After Colon Cancer

Completing treatment is a significant milestone for individuals diagnosed with colorectal cancer. While it brings relief, it can also bring uncertainty about the future and concern over the possibility of recurrence. Others may find themselves managing cancer as a chronic condition, requiring ongoing treatment. No matter where you are in your journey, survivorship comes with unique challenges—and opportunities to take charge of your health^[21].

Creating a survivorship care plan: A survivorship care plan is a crucial tool for post-treatment life. Work with your doctor to develop a plan that includes a schedule for follow-up exams and tests, awareness of potential long-term side effects and when to seek medical attention, recommendations for maintaining overall health, such as nutrition and exercise, and guidelines for cancer screening and preventative care. Staying engaged in your follow-up care can help you feel more in control of your health and detect any issues early^[21].

Follow-up care: Regular follow-ups are essential to monitor for recurrence, new cancers, or late effects of treatment. Follow-up after colorectal cancer treatment varies. Depending on your cancer stage and treatment history, your doctor may recommend colonoscopy, imaging tests, or blood tests^[15][21].

Managing long-term side effects: While most colon cancer survivors won’t need a colostomy, some experience lingering effects of treatment. Understanding and managing these side effects can improve quality of life and overall well-being. Since colon cancer treatments often affect the digestive system, many survivors experience bowel irregularities, including diarrhea, constipation, or changes in bowel control^[21].

Treatment for bowel cancer (colon and rectum) can cause changes to your bowel. These effects can last for a few weeks or months after treatment. Sometimes they might go on for longer^[18].

You might need to look at what you eat and make changes to your diet after treatment for bowel cancer. You may need to experiment a bit to find out which foods upset your system. A dietitian can support you with diet problems from diagnosis, through treatment and afterwards^[18].

Eating well and following a balanced, nutritious diet is one of the best ways you can prepare for colon cancer treatment. Good nutrition is particularly important if you have cancer, but both colon cancer and cancer treatments may interfere with the body’s ability to use and absorb nutrients^[22].

Getting practical and emotional support can help you to cope with a diagnosis of bowel cancer. It can also help you with life during and after treatment. There are many organisations, support groups and other resources to help you cope with bowel cancer and treatment^[18].