All About Colon Cancer
What is the colon?
The colon is the longest part of the large intestine, also known as the large bowel. The large intestine is the last part of the digestive tract. The large intestine is a tube that is about 5 to 6 feet in length. The first 5 feet make up the colon. There are four different parts of the colon: the ascending colon, the transverse colon, the descending colon, and the sigmoid colon. The colon connects to the rectum and finally ends with the anus.
By the time food reaches the colon (about 3 to 8 hours after eating), the nutrients have been absorbed. What remains is liquid waste product. A function of the colon is to change this liquid waste into solid stool. It does this by absorbing water. Stool can spend anywhere from 10 hours to several days in the colon before being expelled through the anus.
What is colon cancer?
Cancer is when cells grow in an uncontrolled way which can lead to a tumor forming. Colon cancer is a malignant (cancerous) tumor that grows in the wall of the colon. Most colon tumors begin when normal tissue in the colon wall forms an adenomatous polyp, or pre-cancerous growth, that comes out of the colon wall. As this polyp grows larger, the tumor forms. This process can take many years, which allows time for early detection with screening tests.
What causes colon cancer and am I at risk?
Colon cancer is the fourth most common type of cancer, in both males and females, in the United States. Every year, an estimated 104,000 cases of colon cancer will be diagnosed in the United States. African Americans, particularly African American men, are at an increased risk. The risk of colon cancer also goes up after age 50, but every year there are more cases reported in those under 50. Colon cancer tends to occur more in ages 55-74 with an average age at diagnosis being 67.
Certain factors put people at higher risk. Individuals with a personal or family history of colon cancer, polyps, or inherited colon cancer syndromes (i.e., FAP and HNPCC/Lynch syndrome), as well as those with ulcerative colitis or Crohn's disease, are all at higher risk and may require screening at an earlier age than the general population. A person with one first degree relative (parent, sibling, or child) with colon cancer is 2 to 3 times as likely to develop colon cancer as someone who does not have an affected relative.
This does not mean that people without a family history are not at risk. Studies of colon cancer cases found that lifestyle factors can put a person at higher risk. These factors include: a diet high in fat and red meat, and low in fruits and vegetables, having a high caloric intake, low levels of physical activity, and obesity. In addition, smoking and excessive alcohol use may play a role in colon cancer development. Despite avoiding all of these factors, some people will still develop colon cancer. With screening and early detection, these patients can be effectively treated in most cases.
How can I prevent colon cancer?
Eating a low-fat diet high in fruits and vegetables and low in red meat, together with regular exercise and maintaining a healthy body weight may help prevent colon cancer. It is also important not to smoke, or to quit if you already smoke. Limiting alcohol may be helpful.
Chemoprevention is defined as “the use of a chemical compound to prevent, inhibit, or reverse the formation of the cancer.” There are ongoing studies looking at vitamins A, E, D, and C, folic acid, calcium, selenium, aspirin, cox-2 inhibitors, statin medications (traditionally used to lower cholesterol), and hormone replacement therapy as potential chemopreventive agents that may prevent or reverse the formation of polyps and colon cancer. These studies have been inconclusive so that specific recommendations cannot be made for the general population. Some of these agents continue to be tested in clinical trials.
What screening tests are used for colon cancer?
When to start screening for colon cancer continues to be under debate. The American Cancer Society recommends that screening for those at average risk begins at age 45. Recently, the US Preventative Task Force also proposed changing the guidelines to begin screening at 45. This continues to be reviewed. Be aware that insurance may not cover screening beginning at age 45. It is important to talk with your provider and insurance company before scheduling your screening test.
There are many different types of screening tests available for colon cancer. Some of these tests look for DNA evidence of cancer in the stool. Others are a visual exam of the colon and rectum via sigmoidoscopy or colonoscopy. You can learn more about the different kinds of tests available on OncoLink. Talk with your healthcare provider about your screening options and how often you will need to have these tests.
Individuals with a family or personal history of colon cancer, inflammatory bowel disease, or genetic syndromes like FAP or HPNCC should have more frequent screenings. Your healthcare provider will advise you on when to begin screening as well as how often you will need to be screened.
What are the signs of colon cancer?
The early stages of colon cancer may not have any symptoms. This is why it is important to have screening tests done even if you feel well. As a polyp grows into a tumor, it may bleed or obstruct the colon, causing symptoms. These symptoms include:
- Bleeding from the rectum.
- Blood in the stool or toilet after a bowel movement.
- A change in the shape of the stool (i.e. thinning).
- Cramping pain in the abdomen.
- Feeling the need to have a bowel movement when you don't actually have to.
These symptoms can also be caused by conditions other than cancer. If you experience these symptoms, you should be checked by a healthcare provider.
How is colon cancer diagnosed?
Once colon cancer is found, further tests are needed to determine the extent of the tumor. The tests used to determine the spread of the tumor are CT scans, MRIs, PET/CT scan and blood tests. Positron Emission tomography (PET) provides a whole-body evaluation and highlights active tumors in the body. Malignant tumors have an increased rate of glycolysis shown by an increased uptake of glucose tracer. PET/CT scan is used to evaluate potentially resectable metastasis in the lung and liver. Carcinoembryonic antigen (CEA) level is a marker for colon cancer that is found in the blood. This marker is elevated in 95% of colon cancer cases.
How is colon cancer staged?
After these tests, a stage is determined to help dictate the necessary treatment. Colon cancer is most commonly staged using the “TNM system.” The TNM staging system assesses the extent of the primary tumor, nodal involvement (describes if there is cancer in the lymph nodes), and distant metastases (if the cancer has spread to other organs). This is reported on your pathology report – you may want to ask for a copy of this report for your personal files. The staging system is very complex. The entire staging system is outlined at the end of this article. Though complicated, the staging system helps healthcare providers determine the extent of the cancer, and in turn, make treatment decisions for a patient's cancer. The stage of cancer, or the extent of the disease, is based on information gathered through the various tests done as the diagnosis and workup of the cancer is being performed.
How is colon cancer treated?
Surgery is the most common treatment for colon cancer. If the cancer is limited to a polyp, you can undergo a polypectomy (removal of the polyp), or a local excision, where a small amount of surrounding tissue is also removed.
If the tumor invades the bowel wall or surrounding tissues, you will require a partial resection. This is the removal of the cancer and a portion of the bowel. Lymph nodes will also be removed to determine if the cancer has spread into them. After the tumor is removed, the two ends of the remaining colon are reconnected, allowing normal bowel function. In some situations, it may not be possible to reconnect the colon, and a colostomy (an opening in the abdominal wall to allow passage of stool) is needed. This may be temporary or permanent.
Despite the fact that a majority of patients have the entire tumor removed by surgery, many individuals will develop a recurrence without further treatment. Chemotherapy is given to reduce this chance of recurrence. The type of chemotherapy used to treat colon cancer can also be influenced by the patient’s ability to tolerate intense chemotherapy, as well as the location of the tumor in the colon and the tumor stage. Your tumor may be tested for specific markers called microsatellite instability (MSI-H) and stability (MSS). This test can indicate sensitivities to certain types of treatments used to treat colon cancer.
Common medications used in the treatment of colon cancer are fluorouracil, oxaliplatin, irinotecan, leucovorin, bevacizumab, trifluridine/tipiracil, capecitabine, and ziv-aflibercept, These medications are used in both initial chemotherapy treatment and in treatment of recurrence/metastatic disease.
Targeted therapies are also used in the treatment of recurrent or metastatic types of colon cancers. These therapies are often used in combination with the previously mentioned chemotherapy medications to target specific abnormalities found in the cancer cells. These abnormalities contribute to the growth, spread, and progression of cancer. Your healthcare provider will test your tumor to determine if a specific target is present.
One such target is epidermal growth factor receptor (EGFR). EGFR is abnormally overexpressed in many cancers (including those of the colon and rectum), so inhibition of EGFR can result in a decrease in tumor cell growth and decreased production of other factors responsible for metastasis (tumor spread). Panitumumab, ramucirumab, and cetuximab are monoclonal antibodies that inhibit binding of epidermal growth factor to EGFR, which prevents epidermal growth factor from working, slowing cancer growth. These agents are generally used for patients whose tumor type is deemed "KRAS wild-type.” This means that there is no mutation with the KRAS protein. Tumors that are KRAS wild type may also be treated with cetuximab and panitumumab. Regorafenib and ramucirumab are medications that target the vascular endothelial growth factor (VEGF). Vemurafenib and encorafenib can target cells that are positive for the BRAF V600E mutation. Trastuzumab, pertuzumab, lapatinib and fam-tratuzumab deruxtecan-nxki may be used in colon cancers with HER2, WRAS, and BRAF mutations.
Immunotherapy is also being used in the treatment of certain colon cancers. Immunotherapy is a method of treating cancer that uses the body’s own capabilities to identify and kill cancer cells. Immunotherapy medications currently being used in the treatment of colon cancer include ipilimumab, nivolumab, and pembrolizumab.
Treatment recommendations for patients with metastatic disease depend on whether the patient is appropriate for intensive therapy. Chemotherapy options for patients with metastatic disease depend on what treatment they initially received. Clinical trial participation may be recommended before standard therapy.
Colon cancer is not typically treated with radiation therapy. If the cancer has invaded another organ, or attached itself to the abdominal wall, radiation therapy may be a treatment option. One reason for the limited role of radiation is that it is a local treatment typically aimed at a "target." Once the colon cancer has been surgically resected, the "target" or high-risk area for disease recurrence is not very easy to define. Furthermore, if the cancer has spread to other organs, chemotherapy (rather than radiation therapy) is able to reach distant areas of spread of tumor cells.
Interventional radiologists (IR) are specialists who use radiology techniques, such as CT scan, to access areas of the body and treat diseases without traditional surgery. These techniques are sometimes called "minimally invasive". In some cases, these providers are able to help patients with colon cancer that has spread (metastasized) to the liver or lung. The techniques currently being used by these specialists include: CT directed biopsies, chemoembolization, radiofrequency ablation, and radioembolization. By entering a patient's blood vessels, the physician can thread a catheter and give treatment directly to the tumor.
Radiofrequency ablation (RFA) is a local treatment that kills the tumor cells with heat while sparing healthy liver or lung tissue. When the tumor is too large or in a location not amenable to RFA, embolization may be used to cut off the blood supply to the tumor, deliver radiation to a tumor (called radioembolization), or combine this technique with chemotherapy to deliver the cancer drug directly to the tumor (called chemoembolization).
Some patients may benefit from having an infusion pump inserted to infuse chemotherapy directly into the liver. IR physicians can also perform palliative procedures, such as inserting a stent to relieve an obstruction, treating certain types of pain, inserting central catheters, or treating blood clots.
There are clinical research trials for most types of cancer, and every stage of the disease. Clinical trials are designed to determine the value of specific treatments. Trials are often designed to treat a certain stage of cancer, either as the first form of treatment offered or as an option for treatment after other treatments have failed to work. They can be used to evaluate medications or treatments to prevent cancer, detect it earlier, or help manage side effects. Clinical trials are extremely important in furthering our knowledge of disease. It is through clinical trials that we know what we do today, and many exciting new therapies are currently being tested. Talk to your provider about participating in clinical trials in your area. You can also explore currently open clinical trials using the OncoLink Clinical Trials Matching Service.
Follow-up Care and Survivorship
Once treatment is completed, you will be followed closely for recurrence. Recommendations for follow up care vary based on the initial stage of your colon cancer. For stages II-IV, you should expect to have examinations with your healthcare provider every 3-6 months for 2 years and then every 6 months for years 2-5. A repeat colonoscopy should be performed 1 year after treatment, then repeated in three years, and then again every 5 years. If the initial colonoscopy shows adenoma, the colonoscopy should be repeated in 1 year. For those with stage, I, II, or III disease routine PET or CT scans are not recommended. For those with stage II/III disease, For those with stage IV disease, CT scans of the chest, abdomen, and pelvis are recommended every 6-12 months for a total of 5 years. CT scans of the chest, abdomen, and pelvis are recommended every 3-6 months for 2 years and then every 6-12 months for a total of 5 years.
Fear of recurrence, relationships and sexual health, long term management of ostomy and body image challenges, the financial impact of cancer treatment, employment issues, and coping strategies are common emotional and practical issues experienced by colon cancer survivors. Your healthcare team can identify resources for support and management of these challenges faced during and after cancer.
Cancer survivorship is a relatively new focus of oncology care. With nearly 17 million cancer survivors in the US alone, there is a need to help patients transition from active treatment to survivorship. What happens next, how do you get back to normal, what should you know and do to live healthy going forward? A survivorship care plan can be a first step in educating yourself about navigating life after cancer and helping you communicate knowledgeably with your healthcare providers. Create a survivorship care plan today on OncoLink.
Resources for More Information
Colon Cancer Alliance - The Colon Cancer Alliance brings the voice of survivors to battle colorectal cancer through patient support, education, research, and advocacy.
Fight Colorectal Cancer - Provides advocacy, education, and support.
The Colon Club - Promotes education and awareness in interesting and out of the box ways.
American Society of Colon and Rectal Surgeons - Society for colon and rectal surgeons and other surgeons dedicated to the treatment of patients with diseases and disorders affecting the colon, rectum, and anus.
Appendix: Complete Colon Cancer Staging
American Joint Committee on Cancer (2017)
Primary tumor cannot be assessed.
No evidence of primary tumor.
Carcinoma in situ, intramucosal carcinoma (involvement of lamina propria with no extension through muscularis mucosae).
Tumor invades the submucosa (through the muscularis mucosa but not into the muscularis propria).
Tumor invades thought the muscularis propria.
Tumor invades through the muscluaris propria into pericolorectal tissues.
Tumor invades the visceral periotoneum or invades or adheres to adjacent organ or structure.
Tumor invades through the viseceral peritoneum (including gross perforaction of the bowel through tumor and continuous invasion of tumor through areas of inflammation to the surface of the visceral peritoneum.
Tumor directly invades or adheres to adjacent organs or structures.
N (Regional Lymph Nodes)
Regional lymph nodes cannot be assessed.
No regional lymph node metastasis.
One to three regional lymph nodes are positive (tumor in lymph nodes measuring ≥0.2mm), or any number of tumor deposits are present and all identifiable lymph nodes are negative.
One regional lymph node is positive.
Two or three regional lymph nodes are positive.
No regional lymph nodes are positive, but there are tumor deposits in the subserosa, mesentery or nonperitonealized pericolic, or perirectal/mesorectal tissues.
Four or more regional nodes are positive.
Four to six regional lymph nodes are positive.
Seven or more regional lymph nodes are positive.
M (Distant Metastasis)
No distant metastasis by imaging; no evidence of tumor in distant sites or organs.
Metastasis to one or more distant sites or organs or peritoneal metastasis is identified.
Metastasis to one site or organ is identified without peritoneal metastasis.
Metastasis to two or more sites or organs is identified without peritoneal metastases.
Metastasis to the peritoneal surface is identified alone or with other site or organ metastases.
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