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Home Science Diseases & Conditions Colon Cancer

What Is Colon Cancer?

Colon cancer is a type of colorectal cancer that affects the colon, also known as the large intestine or large bowel.1,2 The colon is part of the digestive system, also known as the digestive tract—a system of organs that process foods for energy.2 Colon cancer starts when normal cells that line the colon begin to grow and change uncontrollably. These cells eventually form a tumor (which can be benign or malignant) in a process that takes years. Colon cancer is attributable to both genetic and environmental factors. While it’s still a leading cause of death for all genders, recent advancements in screening and therapeutics have improved survivability.3

 

Prevalence of Colon Cancer

In the U.S., the overall risk of developing colorectal cancer (CRC), including both colon cancer and rectal cancer, is about 1 in 23 for those assigned male at birth and 1 in 25 for those assigned female at birth. It’s the third most common cancer diagnosed and the second leading cause of cancer deaths in all genders.3,4

The American Cancer Society estimated that in 2022, there would be more than 106,000 new cases of colon cancer and nearly 45,000 new cases of rectal cancer. Thanks to improvements in screening for colon cancer, there are now more than 1.5 million colorectal cancer survivors in the U.S. Unfortunately, deaths from this cancer among people under the age of 55 (young onset CRC) have increased in recent years.3,4

Causes and Risk Factors

What Causes Colon Cancer?
What Causes Colon Cancer

Researchers have identified several contributing factors to colon cancer, but it's still not clear how exactly they work together to cause colon cancer. These factors include inherited and acquired gene mutations. Environmental factors and dietary choices can also play a role.5

 

Colon Cancer and Genetics

Colorectal cancers can be traced back to DNA mutations that turn off tumor suppressor genes or turn on oncogenes (genes help tumor cells grow and survive). The development of colon cancer usually requires changes in multiple genes.6

About 70% of the time, these mutations are considered sporadic, meaning they occur without a family history of the disease. And 20% of the time, mutations are part of familial clustering, meaning colon cancer is occurring more frequently within a family than one would expect if looking at the rates of the disease in the general population. Finally, about 10% of the time, colon cancer is the product of an inherited syndrome.5

For example, some inherited syndromes associated with colorectal cancer include familial adenomatous polyposis (FAP), attenuated FAP (AFAP) Gardner syndrome, lynch syndrome, Peutz-Jeghers syndrome, and MUTYH-associated polyposis (MAP).6

In many colorectal cancer cases, the first mutation shows up in the APC gene, which helps keep cell growth under control. This mutation leads to an increased growth of colorectal cells.6

Colon Cancer in African Americans, Native Americans, and Ashkenazi Jewish People

Some groups have higher incidence and mortality rates of colorectal cancer, highlighting the need for targeted colon cancer prevention. Among the general population, African Americans have a notably high incidence of colorectal cancer—20% greater than white people--and even higher associated mortality. While some of these differences are tied to a lack of access to screening, care, and other socioeconomic factors, ethnicity-specific factors still exist.7

Native Americans also experience higher incidence rates than non-Hispanic white populations—57.7 versus 41.8 per 100,000 in people who were assigned male at birth and 44.6 versus 32.7 per 100,000 in people who were assigned female at birth.8 Some people of Ashkenazi Jewish heritage are also at a significantly higher risk of developing colorectal cancers because of an inherited genetic mutation called APC I1307K.9

 

Colon Cancer and the Environment

Colon cancer has been linked to low levels of physical activity, frequent meal intake, low-fiber diets, low levels of dietary calcium, and low beta carotene intake.10

Overall, about 90% of colorectal cancers are caused by environmental exposures, such as a low-fiber and high-fat diet, alcohol consumption, and tobacco use, which occurred decades before a patient was diagnosed. Researchers recently linked dietary metabolites to a protective or procarcinogenic environment in the colon. This environment is modulated by a person's microbiome.11

Colon Cancer Detection
  • Colon cancer screening identifies early cancers and polyps (abnormal growths) in the large intestine, often leading to treatment before cancer can spread. Regular screenings are an effective way to reduce potential complications or death from colon cancer and colorectal cancer.12,13

    Almost all colorectal cancers begin as precancerous polyps. These polyps are often asymptomatic and can be present for many years before cancer that is more invasive develops. Screening allows a doctor to find and remove polyps before they turn cancerous.13 It’s especially important for people with a family history of colorectal cancer.14 According to the American Cancer Society guidelines for CRC screening tests, people should begin regular screenings at age 45. Depending on a person’s health and life expectancy, the decision to be screened and the recommended frequency varies.14

  • While researchers are still investigating whether diet can reduce colorectal cancer risk factors, experts recommend a diet that is low in animal fats and high in whole grains, fruits, and vegetables.13

    Researchers have also found that some medicines, such as low-dose aspirin, can help prevent colorectal cancer in some adults, depending on their risk factors and age. Experts also recommend getting physical activity, limiting alcohol, and avoiding tobacco products.13

Types of Colon Cancer

Typically starting with a polyp, colorectal cancer has a different name depending on whether it starts in the colon (colon cancer) or the rectum (rectal cancer).3

The types of colon cancer include:

  • Adenocarcinomas of the large intestine are a type of tumor that arises in the epithelial tissue of the colon or rectum.15 The majority of colorectal cancer cases are carcinomas, and of that group, more than 90% are adenocarcinomas.5

  • These develop in nerve cells known as neuroendocrine cells.5,16

  • These are a type of non-Hodgkin's lymphoma.5,17

  • These form in cells lining the gastrointestinal tract.5,18

  • These form in the muscles that guide waste through a person's digestive tract.19,20

  • These are extremely rare, accounting for fewer than 1% of all instances of colorectal cancer. Surgery is the typical treatment.5,21

  • These typically begin to affect people in their teenage years and result in the development of hundreds or even thousands of polyps in the intestine.5,22

Colon Cancer Symptoms

Colorectal cancers and polyps are frequently asymptomatic, especially early in their progression. When symptoms do emerge, they often show up as:23

  • Changes in bowel habits
  • Constipation, diarrhea, or a feeling the bowel is not emptying
  • Blood in stool
  • Pain in the abdomen, along with aches or cramps that don't resolve on their own
  • Unexplained weight loss

Abdominal pain and bowel issues aren't the only symptoms that the disease presents. Iron deficiency, with or without anemia, has been found to be the most frequent hematological manifestation in patients with cancer, particularly colorectal cancer.24

Colon Cancer Symptoms

Colon Cancer Complications

Colon cancer complications can be serious. They include perforation of the colon, obstruction, and bleeding.25

When untreated, colorectal cancer can cause bowel obstruction, can spread cancer to other tissues or organs (metastasis), and can develop into second primary colorectal cancer.26

Colon Cancer Complications
The Importance of Colon Cancer Screening

As science evolves, screening for colorectal cancer becomes even more beneficial.5

Currently, the U.S. Preventative Task Force recommends screening for adults aged 45 to 75. After this age range, screening decisions are made on an individual basis. Patients should work with their doctors to determine when to start screening, which tests to take, and how to set up an ideal testing schedule.

Patients and their doctors have several screening tests to choose from, including stool tests, flexible sigmoidoscopy, CT colonography, and colonoscopy.

Every test has pros and cons. Patients should talk to their doctors about which tests to take. Decisions will depend on preferences, medical conditions, available resources, and the likelihood a patient will complete a test.27

This test involves the use of a long, thin, flexible tube with a light on it to check for both polyps and cancer in the rectum and colon. Doctors are able to remove most polyps and even some cancers during the screening. Colonoscopies can also be used as a follow-up test if a doctor finds anything unusual during other screening tests. Colonoscopies are generally performed every 10 years for anyone who does not have an increased risk of colorectal cancer.27

Stool tests come in three forms:27

  • Guaiac-based fecal occult blood test (gFOBT). This colon cancer blood test uses a chemical to detect blood in stool and is performed once a year. It’s done at home using a test that comes from a healthcare provider.
  • Fecal immunochemical test (FIT). This at-home test detects blood in stool using antibodies and is performed once a year.
  • The FIT-DNA test (stool DNA test). This at-home test is a combination of a FIT and a test that detects altered DNA in stool. It collects an entire bowel movement for testing. This test is performed once every three years.
  • Cologuard. This at-home test is more expensive than a FIT and is about 92% accurate in detecting colorectal cancer. It looks for blood in stool but also searches for DNA markers of precancerous polyps and colon cancer.28,29

Like colonoscopy, flexible sigmoidoscopy uses a thin, flexible, tube and light. However, the shorter tube with flex sigmoid focuses only on the lower third of the colon. The tube is inserted into the patient's rectum to check for polyps or cancer. It's performed every five years, or every 10 years with a FIT each year.27

Also known as a virtual colonoscopy, this test uses X-rays and computers to examine the entire colon. The images are displayed on a computer for a doctor to review.27

Diagnosis and Treatment

Colon Cancer Diagnosis

Diagnosis of colorectal cancer often begins with a screening to evaluate whether symptoms point to cancer. If a gastroenterologist suspects colorectal cancer, a biopsy is recommended and then performed during a colonoscopy. During the colonoscopy, a doctor will remove a small sample of tissue with a tool that is passed through the scope. In less common cases, part of the colon might need to be surgically removed to make a diagnosis.30, 31, 32

Samples are then sent to the lab for examination. If cancer is found, other tests might be performed to more accurately classify the cancer and determine treatment options. Those tests may include biomarker testing, which is routine in assessing colorectal cancer. This type of testing provides oncologists with more information about the type of cancer they are treating by examining genes, proteins, or other pieces of biological information, all of which are known as biomarkers.30, 31, 32

These biomarkers provide clues as to how cancer develops. With this information, oncologists can take a more targeted approach to treating each case of colorectal cancer. More targeted treatments can lead to better treatment outcomes for people with colorectal cancer.31

For example, a doctor will likely order biomarker tests—such as for mutations of the genes KRAS, NRAS, and BRAF—to determine which drugs may be considered for treatment. A doctor might also order microsatellite instability (MSI) and mismatch repair (MMR) testing to check for a possible connection with Lynch syndrome.32

Colon Cancer Stages

If a polyp indicates a colon cancer diagnosis, a doctor might also send for additional imaging tests for colorectal cancer, such as a CT scan. The tests help confirm and determine colon cancer staging, which indicates how far the cancer has spread.32

  • These cancers tend to be confined to the colon walls, but in Stage 2 can also spread to tissue that lines other organs such as the abdomen.

  • The colon cancer has spread to nearby lymph nodes.

  • Also known as metastatic colon cancer, the cancer has spread to distant organs, like the lungs or liver.33,34

Colon Cancer Treatment

Once someone is diagnosed with colon cancer, there are multiple questions that need to be answered before a physician can determine colon cancer prognosis, treatment, medications, and dietary and lifestyle management changes.

Treatment for colon cancer will depend heavily on colon cancer staging.34 In general, treatments involve a mix of surgery, medication, and lifestyle adjustments.

  • In this stage, since the cancer hasn't grown past the inner lining of the colon, polyps are removed during a colonoscopy.34

  • Treatment for this stage of cancer can involve removing a polyp. If the cancer has not spread to the edges of the removed tissue, it’s possible that no further treatment is required. If the polyp is high grade is high grade, or if cancer cells are found on the edge of the biopsy, then more surgery might be needed. Additional surgery might be required if the polyp couldn't be removed completely or if it was removed in multiple pieces.34

  • Cancers in this stage have often grown through the wall of the colon and possibly into nearby tissue. Removing the section of the colon along with lymph nodes nearby might be the only treatment necessary. In some cases, doctors might recommend chemotherapy after surgery (adjuvant chemotherapy) if they believe the cancer has a high risk of returning. This could be because:34

    • The cancer looks highly abnormal when viewed in the lab.
    • The cancer caused a hole in the colon wall.
    • The cancer has obstructed the colon.
    • The cancer has grown into lymph or blood vessels.


    A doctor might also recommend testing for MSI or MMR gene changes to decide whether adjuvant chemotherapy would be helpful. If chemotherapy is used, the most likely options include 5-FU and leucovorin, oxaliplatin, or capecitabine. Other combinations are available, too.34

  • Since this stage involves cancers that have spread to lymph nodes, the standard treatment is surgery to remove the affected sections of the colon and lymph nodes, and adjuvant chemotherapy. Chemotherapy regimens are most often FOLFOX (5-FU, leucovorin, and oxaliplatin) or CAPEOX (capecitabine and oxaliplatin). Depending on their age and health needs, some patients receive 5-FU with leucovorin or capecitabine alone.34

    For advanced cancers that can't be removed with surgery, chemoradiation (chemotherapy given along with radiation) could be recommended.34

  • At this stage, the cancer has spread to distant organs and tissues. Colon cancers spread most often to the liver. But they can also migrate to other areas, like the brain, lungs, distant lymph nodes, or the lining of the abdominal cavity. In these cases, colon cancer surgeries are unlikely to be effective. However, if the cancer has only metastasized to a few areas in the lungs or liver, surgery may extend life or prevent spread. Chemotherapy for colon cancer is often administered after surgery. Hepatic artery infusion is used in some cases where cancer has spread to the liver.34

    Research is informing a class of drugs that target specific changes in the cells responsible for rectal or colon cancer. A class of drugs that differs from chemotherapy (chemo), targeted therapies may be effective when chemo fails. Physicians can prescribe targeted therapies alone or in conjunction with chemo. They also may come with a different set of side effects.35

    Biomarker testing can help identify appropriate targeted therapy options for a particular patient, given their gene mutation and type of cancer. Biomarker testing may also point to the presence of an aggressive disease or prognosis.31

    Some people who have advanced colorectal cancer may benefit from immunotherapy depending on which mutation they have and what stage their cancer is in. Unlike other treatments, which directly target cancer cells, immunotherapy prompts the immune system to attack and eliminate cancer cells.36

Colon Cancer Diet Questions

Nutrition can be a powerful secondary tool in supporting cancer treatment options. Eating well may boost energy reserves and help the body fight against infection. Additionally, a good diet during cancer treatment may help to cope better with side effects or handle stronger doses of certain medicines. 

Trying some new foods during treatment might reveal that some things may taste better while receiving therapy. The American Cancer Society recommends experimenting with eating more plant-based foods and try to consume fruits and vegetables daily in a variety of colors. They also suggest trying to avoid processed foods, sugary drinks, and processed meats.37

Global Impact of Colon Cancers

According to recent colon cancer statistics, colorectal cancers are a leading cause of death and illness across the globe. In the U.S., they make up 11% of all cancer treatment costs, the second highest for any cancer in the country.38

Colorectal cancers are estimated to be the third most common cancer and the second most deadly cancer, with an incidence of 1.9 million cases and just under 1 million deaths worldwide in 2020. This cancer is more common in highly developed countries, though it’s increasing in low- and middle-income countries. The world is also experiencing an increase in early-onset colon cancers. The same statistics report notes that the number of new cases is projected to rise to 3.2 million by 2040, based on estimations of human development, aging, and population growth.39

Global Impact of Colon Cancers

Frequently Asked Questions About Colon Cancer

  • Survival rates can offer an idea of what percentage of people with the same type and stage of cancer are still alive a certain amount of time (such as 5 years) after they were diagnosed. They determine how long someone will live, but they may help to give a better understanding of how likely it is that treatment will be successful. The survival rate for colorectal cancer varies depending on the stage, ranging from 91% for localized cancers to 14% for distant ones. For rectal cancer, the rates range between 90% and 17%.40

  • Colon cancer is highly treatable and frequently curable when it's localized to the bowel. But recurrence after surgery is a significant problem.41

  • Most colon cancers are not hereditary, but a number of syndromes are associated with an increased risk of cancer. These include Lynch syndrome, familial adenomatous polyposis (FAP), and attenuated familial adenomatous polyposis (AFAP).5,6

  • Often, colorectal cancer is slow-growing, beginning as a polyp. If left alone for many years, it can become cancerous. But early removal may stop this.42

  • Most often, polyps in the rectum and colon are not cancerous.43 Research demonstrates that as polyps increase in size, the incidence of cancer increases.44

  • The lifetime risk for developing colorectal cancer is approximately 1 in 23 (4.3%) for those with people who were assigned male at birth and 1 in 25 (4%) for those assigned female at birth. Colorectal cancer is the third leading cause of cancer deaths for all genders.4

  • Many drugs are approved for colon cancer treatment. Cancer.gov provides a list of drugs and drug combinations used for colon cancer, rectal cancer, and gastroenteropancreatic neuroendocrine tumors.45

Learn More About Colon Cancer

Find a Pfizer clinical trial for colon cancer at PfizerClinicalTrials.com.

Explore colon cancer clinical trials at ClinicalTrials.gov.

Area of Focus: Oncology

Colon Cancer is a focus of Pfizer’s Oncology Therapeutic Area. Visit the Oncology Page.

The information contained on this page is provided for your general information only. It is not intended as a substitute for seeking medical advice from a healthcare provider. Pfizer is not in the business of providing medical advice and does not engage in the practice of medicine. Pfizer under no circumstances recommends particular treatments for specific individuals and in all cases recommends consulting a physician or healthcare center before pursuing any course of treatment.

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