Colon cancer is a form of colorectal cancer which combines cancers originating in both the colon and rectum. Most colon cancers are adenocarcinomas, beginning with a benign growth, or polyp, on the inside lining of the colon that eventually becomes cancerous.
As one of the leading causes of cancer-related deaths in the U.S., one in 22 men and one in 24 women will be diagnosed with colon cancer in their lifetime. It is estimated that 135,430 people will be diagnosed and 50,260 people will die from the disease be the end of 2017.
Causes and Risk Factors
Colon cancer, like all cancers, is brought on by changes in the DNA of cells. These changes can either be acquired gene mutations (where the cell changes over time) or inherited gene mutations (passed down hereditarily).
While it is not always clear what causes colon cancer, there are a number of risk factors that increase your chance of the disease. These include:
- Obesity and inactivity: Carrying excess weight or being obese, and not leading an active lifestyle increases a person’s risk of developing colon cancer.
- Diet: Eating a lot of processed meats (like hot dogs and lunch meats) and red meats (like beef, pork, and lamb) may lead to colon cancer. Diets high in vegetables and whole grains are linked with a lower risk of the disease.
- Tobacco and alcohol: Heavy alcohol consumption is linked to an increased risk of the disease. Although smoking most commonly leads to lung cancer, it also has been proven to increase the risk of colon cancer.
- Age: As you age, your risk of colon cancer increases. Many doctors recommend regular screenings starting at the age of 50.
- Ethnicity: African Americans and people of Ashkenazi Jewish descent have the highest risk of developing colon cancer of any racial group. The reasons for this are still unknown.
- Genetics: Between 5% and 10% of people diagnosed with colon cancer inherit a gene mutation from family members. Most commonly, these inherited mutations are familial adenomatous polyposis (FAP) or Lynch syndrome (hereditary non-polyposis colorectal cancer, or HNPCC).
- Family history: One in five colon cancer patients have other family members with the disease. If you have family members, particularly immediate members (like a parent, child, or sibling), with colon cancer, your doctor may recommend more frequent cancer screenings.
- History of cancer: If you have a history of adenomas (benign growths), you have a higher risk that these will develop into cancerous growths in the colon. Some studies also show that men previously treated for testicular cancer or prostate cancer have a higher risk of developing colon cancer. This may be related to the use of radiation in their treatment.
- Diabetes: People with type-2 diabetes are more likely to develop colon cancer than those without. This may be due in part to an increased likelihood of obesity and inactivity.
- Inflammatory bowel disease: People afflicted with inflammatory bowel disease (IBD), including Crohn’s disease or ulcerative colitis, are more likely to develop colon cancer. This is likely due to the consistent inflammation of the colon. If you suffer from IBD, you may need to be screened more frequently, and start screenings at an earlier age.
Symptoms of Colon Cancer
In the early stages of colon cancer, patients often experience few or no symptoms, making regular screenings very important.
Since colon cancer affects the large intestine, the organ responsible for absorbing nutrients from food and helping the body to rid itself of waste, most symptoms of the disease relate to changes in the patient’s weight and bowel movements. If you or someone you love is experiencing any of the following symptoms of colon cancer, speak to your healthcare provider.
- Unintended weight loss
- Change in bowel habits (including diarrhea or constipation) that last more than four weeks
- Change in the consistency of stool (including very thin stools) that lasts more than four weeks
- Persistent bowel pain
- Rectal bleeding or bloody stool
- Cramping, abdominal pain, or bloating
Preventing Colon Cancer
There is no guaranteed way to prevent colon cancer. But certain lifestyle choices and other considerations can reduce your risk of developing the disease.
Regular screening: Regular colonoscopies are the best ways to catch colon irregularities early and effectively. It takes about 10 to 15 years for polyps to grow cancerous growths, so getting a colonoscopy every 10 years after the age of 50 can help catch abnormalities before they advance to malignant tumors. Your doctor may recommend other screening methods, like a stool DNA test or double-contrast barium enema. They may also recommend you be screened more regularly, particularly if you are at high-risk of the disease.
Lifestyle choices: Living a healthy lifestyle can reduce your risk of colon cancer. This includes eating a balanced diet, getting regular exercise, and avoiding excessive alcohol and tobacco consumption.
Non-steroidal anti-inflammatory drugs (NSAIDs): Some studies suggest that regularly taking NSAIDs, such as aspirin and ibuprofen, can lower the risk of colon cancer. But many doctors don’t recommend this method as frequent NSAID usage can lead to other health complications. Talk to your doctor before beginning a regular NSAID regimen.
Colon Cancer Diagnosis and Types
As with many types of cancer, the earlier you detect colon cancer, the higher the chance of recovery. Regular screenings, especially after the age of 50, are crucial to diagnosing and treating the disease.
Diagnostic Tests for Colon Cancer
The following methods are most commonly used to test for colon cancer, although some other tests are available.
Colonoscopy: The primary test for colon cancer, a colonoscopy is a full examination of the intestine using a colonoscope, a thin tube equipped with a small video camera. Doctors will be able to check for any suspicious growths and polyps, and later test the tissue using a biopsy to screen for cancer.
Flexible sigmoidoscopy: Less invasive than a colonoscopy, doctors examine the rectum and the lower part of the colon using a tube with a light and camera called a sigmoidoscope. As the scope does not explore the entire colon, it is primarily used to diagnose rectal cancer.
Fecal occult blood test: This test examines the presence of blood in stool by using a chemical reaction. As this test can sometimes result in a false positive, doctors will likely want to administer a secondary test, like a colonoscopy, to provide a more accurate diagnosis.
Types of Colon Cancer
The majority of colon cancers are adenocarcinomas, but there are more rare types of the disease, including the following:
Colorectal adenocarcinoma: A growth or polyp in the colon lining turns cancerous and becomes an adenoma.
Gastrointestinal carcinoid tumors: These tumors develop slowly in nerve cells that regulate hormones, called neuroendocrine cells.
Primary colorectal lymphomas: These tumors develop in lymph nodes, but can occasionally grow in the colon.
Stages of Colon Cancer
After diagnosing the disease, doctors will perform additional tests to establish the stage of the cancer (the extent that it has spread in the body). These tests aim to determine the growth within the intestine, and assess whether the cancer has spread to nearby lymph nodes or other organs through metastasis.
Stage 0: The cancer is in its earliest stage and is at its most treatable. It exists only in the inner layer (mucosa) of the intestine
Stage I: The cancer has grown outside of the mucosa into the submucosa. It has not spread to nearby lymph nodes
Stage II: The cancer has spread to or beyond the outermost layer of the colon but has not spread to nearby lymph nodes
Stage IIA: The cancer has spread into the outermost layer of the colon but has not yet gone beyond the wall
Stage IIB: The cancer has spread outside the wall of the colon
Stage IIC: The cancer has grown outside the wall and attached itself to nearby sites or organs
Stage III: The cancer has spread to nearby lymph nodes but has not reached distant sites, like the lungs or liver
Stage IIIA: The cancer has spread into the submucosa and to one to six lymph nodes
Stage IIIB: The cancer has spread to the outermost layer of the colon and to one to six lymph nodes
Stage IIIC: The cancer has grown through the outermost layer and spread to four or more lymph nodes and may have attached to nearby organs
Stage IV: At its most advanced and aggressive stage, the cancer has metastasized and spread to distant organs
Stage IVA: The cancer has spread to one distant organ. It may or may not have spread within the colon and to lymph nodes
Stage IVB: The cancer has spread to more than one distant organ or to distant lymph nodes. It may or may not have spread within the colon and to lymph nodes
Colon Cancer Survival Rate and Life Expectancy
According to the American Cancer Society, colon cancer is one of the leading causes of death in the U.S. It is the third leading cause of cancer-related deaths in American women, and the second leading cause in American men.
While it remains a leading cause of death, the death rate of colon cancer patients has steadily dropped over the last few decades. Currently, there are more than 1 million colon cancer survivors in the U.S. This can be attributed to advancements in treatments over the years, as well as more frequent screenings leading to earlier medical intervention.
The survival rate of colon cancer depends on the stage at which treatment begins, with patients diagnosed early having a higher chance of survival. That’s why it’s important to seek medical help immediately if you or someone you care about is showing symptoms of colon cancer.
|Colon Cancer Stage||5-Year Survival Rate|
Colon Cancer Treatments and Therapies
Treatment will depend on the stage of the cancer, and will often consist of a combination of methods. At most stages, treatment will involve surgery to remove the tumor. For early stage colon cancers (stage 0-I), surgery may be the only treatment needed, as the cancer has not yet spread.
In addition to surgery, some cases may require:
Chemotherapy: Drugs are administered to destroy cancer cells or prevent them from spreading. Chemotherapy is usually not necessary for patients with stage 0, I, or II colon cancer, but can be a successful treatment method in stage III or IV. Typically, treatment consists of a combination of different chemo drugs, including:
- 5-Fluorouracil (5-FU)
- Capecitabine (Xeloda)
- Oxaliplatin (Eloxatin)
- Trifluridine and tipiracil (Lonsurf)
Radiation: Often used after surgery, doctors will use high-powered and highly targeted rays to destroy remaining cancer cells, especially if the cancer is in the lining of the abdomen or another internal organ.
Targeted therapy: New drugs are being developed to target aspects of the cancer molecule and stop the disease from spreading by inhibiting the survival of the cell. There are a number of drug options currently available to many patients, including Cetuximab, Panitumumab, Bevacizumab, Ramucirumab, Ziv-aflibercept, and Regorafenib.
Immunotherapy: This therapy targets the patient’s immune system to make it recognize and destroy cancerous cells. There are a few approved immunotherapy drugs available that show promise for the treatment of colon cancer. These include Bevacizumab, Cetuximab, Ramucirumab, and Panitumumab.
Treatments for patients in the late stages of cancer are more complex and aggressive, and are not always effective. To catch colon cancer when it is in the early stages and most easily treatable, remember to attend regular screenings, and let your doctor know if you experience any concerning symptoms.