Colon cancer is cancer that affects the large intestine (colon), which is the last part of your digestive tract. Most colon cancer begin as small, benign clumps of cells called adenomatous polyps. However, some of these polyps can become colon cancers over time.
Polyps may be small and may show little or no symptoms. Therefore, regular screening is advised to help detect or prevent colon cancer by identifying and removing polyps before they turn cancerours.
Symptoms of Colon cancer
Signs and symptoms of colon cancer include:
- A change in your bowel habits, including diarrhea or constipation
- Blood in your stool
- Persistent abdominal pain
- Unexplained weight loss
- A feeling that your bowel doesn’t empty completely
- Weakness or fatigue
Many people with colon cancer experience no symptoms in the early stages of the disease. When symptoms appear, they’ll likely vary, depending on the size and location of the cancer in your large intestine.
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Causes of Colon Cancer
In most cases, it’s not clear what causes colon cancer. Doctors know that colon cancer occurs when healthy cells in the colon develop faults in their genetic design, the DNA.
Healthy cells grow and divide in an systematic way to keep your body functioning normally. But when a cell’s DNA is destroyed and becomes cancerous, cells continue to divide, even when new cells aren’t needed. The accumulated cells later form a tumor.
With time, the cancer cells can grow to attack and destroy nearby normal tissue. And cancerous cells can travel to other parts of the body to form deposits there (metastasis).
Inherited gene mutations that increase the risk of colon cancer
Inherited gene mutations that increase the risk of colon cancer can be passed through families, but these inherited genes are connected to only a small percentage of colon cancers. Inherited gene mutations don’t make cancer inescapable, but they can increase cancer risk of a person.
The most common forms of inherited colon cancer syndromes are:
- Hereditary nonpolyposis colorectal cancer (HNPCC).HNPCC, also called Lynch syndrome, increases the risk of colon cancer and other cancers. People with HNPCC have a tendency to to develop colon cancer before age 50.
- Familial adenomatous polyposis (FAP).FAP is a rare ailment that causes you to develop thousands of polyps in the lining of your colon and rectum. People with untreated FAP are highly at risk of developing colon cancer before age 40.
FAP, HNPCC and other, rarer inherited colon cancer syndromes can be detected through genetic testing.
Link between diet and increased colon cancer risk
Studies of large groups of people have shown a link between a typical Western diet and an increased risk of colon cancer. A typical Western diet is low in fiber and high in fat.
When people move from areas where the usual diet is low in fat and high in fiber to areas where the typical Western diet is most common, the risk of colon cancer in these people increases expressively. It’s not clear why this happens. Scientists are studying whether a high-fat, low-fiber diet affects the microbes that live in the colon or causes basic inflammation that may contribute to cancer risk.
Factors that may increase your risk of colon cancer include:
- African-American race.African-Americans have a greater risk of colon cancer than people of other races.
- Older age.Colon cancer can occur in younger people, but it occurs much less frequently. People older than 50 are mostly diagnosed with colon cancer.
- A personal history of colorectal cancer or polyps.If you’ve already had colon cancer or adenomatous polyps, you have a greater risk of colon cancer in the future.
- Inflammatory intestinal conditions.Such as Crohn’s disease and ulcerative colitis, can increase a person’s risk of colon cancer.
- Inherited syndromes that increase colon cancer risk.Genetic syndromes passed through generations of your family can increase your risk of colon cancer. These syndromes include familial adenomatous polyposis and hereditary nonpolyposis colorectal cancer, which is also known as Lynch syndrome.
- Family history of colon cancer.You’re more likely to develop colon cancer if you have a parent, sibling or child with the disease. If more than one family member has colon cancer or rectal cancer, your risk is even greater.
- Low-fiber, high-fat diet.Colon cancer and rectal cancer may be associated with a diet low in fiber and high in fat and calories. Research in this area has had mixed results. Some studies have found an increased risk of colon cancer in people who eat diets high in red meat and processed meat.
- A sedentary lifestyle.If you’re inactive, you’re more likely to develop colon cancer. Getting regular physical activity may help reduce risk.
- People with diabetes and insulin resistance have a high risk of colon cancer.
- People who are obese or overweight have an increased risk of colon cancer than people of normal weight.
- People who smoke may have an increased risk of colon cancer.
- Excessive drinkers of alcohol are more at risk of developing colon cancer.
- Radiation therapy for cancer.Radiation therapy directed at the abdomen to treat previous cancers increases the risk of colon and rectal cancer.
Get screened for colon cancer
People with an increased risk, such as those with a family history of colon cancer, should consider early screening. Several screening options exist, each with its own benefits and disadvantages. Talk about your doctor about your options to decide which tests are right for you.
Make lifestyle changes to reduce your risk
- Eat fruits, vegetables and whole grains.Fruits, vegetables and whole grains contain vitamins, minerals, fiber and antioxidants, which may play a vital role in preventing cancer. Choose a variety of fruits and vegetables so that you get an array of vitamins and nutrients.
- Drink alcohol in moderation.If you choose to drink alcohol, limit the amount of alcohol you drink to no more than one drink daily for women and two for men.
- Stop smoking.
- Exercise most days of the week.
- Maintain a healthy weight.
Colon cancer prevention for people with a high risk
Some medications have been found to reduce the risk of precancerous polyps or colon cancer. However, not enough evidence exists to recommend these medications to people who have an average risk of colon cancer. For instance, some evidence links a reduced risk of polyps and colon cancer to regular use of aspirin or aspirin-like drugs. But it’s not clear what dose and what length of time would be needed to reduce the risk of colon cancer. Taking aspirin daily has some risks, including gastrointestinal bleeding and ulcers, so doctors don’t recommend this as a prevention approach unless you have a high risk of colon cancer.
Screening for colon cancer
Doctors recommend certain screening tests for healthy people with no signs or symptoms in order to look for early colon cancer. Finding colon cancer at its early stage provides the greatest chance for a cure. Screening has been shown to reduce your risk of dying of colon cancer.
People with an average risk of colon cancer can consider screening beginning at age 50. But people with an increased risk, such as those with a family history of colon cancer, should consider screening sooner. African-Americans and American Indians may consider beginning colon cancer screening at age 45.
Diagnosing colon cancer
If your signs and symptoms indicate that you could have colon cancer, your doctor may recommend one or more tests and procedures:
- Clonoscopy: This method uses a long, flexible scope attached to a video camera and monitor to examine the inside of your colon. If any suspicious areas are found, your doctor can pass surgical tools through the tube to take tissue samples (biopsies) for analysis.
- Blood tests.No blood test can tell you if you have colon cancer. But your doctor may test your blood for clues about your overall health, such as kidney and liver function tests.
Your doctor may also test your blood for a chemical sometimes produced by colon cancers (carcinoembryonic antigen or CEA). Tracked over time, the level of CEA in your blood may help your doctor understand your prognosis and whether your cancer is responding to treatment.
Stages of colon cancer
Once you’ve been diagnosed with colon cancer, your doctor will order tests to determine the extent (stage) of your cancer. Staging helps determine what treatments are most appropriate for you.
Staging tests may include imaging procedures such as abdominal, pelvic and chest CT scans. In many cases, the stage of your cancer may not be determined until after colon cancer surgery.
The stages of colon cancer are:
- Stage I.The cancer has grown through the superficial lining (mucosa) of the colon or rectum but hasn’t spread beyond the rectum.
- Stage II.The cancer has grown into or through the wall of the colon or rectum but hasn’t spread to nearby lymph nodes.
- Stage III.The cancer has invaded nearby lymph nodes but isn’t affecting other parts of your body yet.
- Stage IV.The cancer has spread to distant sites, such as other organs — for instance, to your liver or lung.
The type of treatment your doctor recommends will depend largely on the stage of your cancer. The three primary treatment options are surgery, chemotherapy and radiation.
Surgery for early-stage colon cancer
If your colon cancer is very small, your doctor may recommend a minimally invasive approach to surgery, such as:
- Removing polyps during a colonoscopy.If your cancer is small, localized and completely contained within a polyp and in a very early stage, your doctor may be able to remove it completely during a colonoscopy.
- Endoscopic mucosal resection.Removing larger polyps may require also taking a small amount of the lining of the colon or rectum in a procedure called an endoscopic mucosal resection.
- Minimally invasive surgery.Polyps that can’t be removed during a colonoscopy may be removed using laparoscopic surgery. In this procedure, your surgeon performs the operation through several small incisions in your abdominal wall, inserting instruments with attached cameras that display your colon on a video monitor. The surgeon may also take samples from lymph nodes in the area where the cancer is located.
Surgery for invasive colon cancer
If the cancer has grown into or through your colon, your surgeon may recommend:
- Partial colectomy.The surgeon removes the part of your colon that contains the cancer, along with an edge of normal tissue on either side of the cancer. Your surgeon is often able to rejoin the healthy portions of your colon or rectum. This procedure can commonly be done by a minimally invasive approach (laparoscopy).
- Surgery to create a way for waste to leave your body.When it’s not possible to relink the healthy portions of your colon or rectum, you may need an ostomy which involves creating an opening in the wall of your abdomen from a portion of the remaining bowel for the removal of stool into a bag that fits securely over the opening.
Sometimes the ostomy is only temporary, allowing your colon or rectum time to heal after surgery. In some cases, colostomy may be permanent.
- Lymph node removal.Nearby lymph nodes are usually also removed during colon cancer surgery and tested for cancer.
Chemotherapy uses drugs to destroy cancer cells. Chemotherapy for colon cancer is usually administered after surgery if the cancer has spread to lymph nodes. Chemotherapy may help reduce the risk of cancer returning and death from cancer. Sometimes chemotherapy may be used before surgery as well, with the aim of shrinking the cancer before an operation. Chemotherapy can also be given to ease symptoms of colon cancer that has spread to other areas of the body.
Radiation therapy uses powerful energy sources, such as X-rays, to kill cancer cells, to shrink large tumors before an operation so that they can be easily removed, or to relieve symptoms of colon cancer and rectal cancer. Radiation therapy either alone or combined with chemotherapy is one of the best treatment options for the initial management of rectal cancer followed by surgery.
Targeted drug therapy
Drugs that target specific malfunctions that allow cancer cells to grow are available to people with advanced colon cancer, including:
- Bevacizumab (Avastin)
- Cetuximab (Erbitux)
- Panitumumab (Vectibix)
- Ramucirumab (Cyramza)
- Regorafenib (Stivarga)
- Ziv-aflibercept (Zaltrap)
Targeted drugs can be given along with chemotherapy or alone. Targeted drugs are typically reserved for people with advanced colon cancer.
Some people are helped by targeted drugs, while others are not. Researchers have recently made progress in determining who is most likely to benefit from specific targeted drugs. Until more is known, doctors carefully weigh the possible benefit of targeted drugs against the risk of side effects and the cost when deciding whether to use these treatments.
Some patients with advanced colon cancer have a chance to benefit from immunotherapy with antibodies such as pembrolizumab (Keytruda) and nivolumab (Opdivo). Whether a colon cancer has the chance to respond to these immunotherapies can be determined by a specific test of the tumor tissue.
Supportive (palliative) care
Palliative care is specialized medical care that focuses on providing relief from pain and other symptoms of a serious illness. Palliative care specialists work with you, your family and your other doctors to provide an extra layer of support that complements your ongoing care.
When palliative care is used along with all of the other appropriate treatments, people with cancer may feel better and live longer.
Palliative care is provided by a team of doctors, nurses and other specially trained professionals. Palliative care teams aim to improve the quality of life for people with cancer and their families. This form of care is offered alongside curative or other treatments you may be receiving.