Colon cancer starts in the large intestine and spreads to the colon (colon). The last part of the digestive tract is the colon.
Colon cancer is most common in older people, but it can happen to anyone at any age. It usually starts with small, noncancerous clumps of cells on the inside of the colon called polyps. Some of these polyps can turn into colon cancer over time.
Polyps may be small and cause little or no pain. Because of this, doctors recommend getting regular screening tests to find polyps and get rid of them before they turn into cancer.
If colon cancer starts to grow, there are many ways to treat it, such as surgery, radiation therapy, and drug treatments like chemotherapy, targeted therapy, and immunotherapy.
Colorectal cancer is a term that combines colon cancer and rectal cancer, which starts in the rectum and spreads to the colon.
- A persistent change in your bowel habits, including diarrhea or constipation or a change in the consistency of your stool
- Rectal bleeding or blood in your stool
- Persistent abdominal discomfort, such as cramps, gas or pain
- A feeling that your bowel doesn’t empty completely
- Weakness or fatigue
- Unexplained weight loss
In the early stages of colon cancer, many people don’t have any signs or symptoms. When symptoms show up, they may be different depending on how big the cancer is and where it is in the large intestine.
When to see a doctor
If you notice any persistent symptoms that worry you, make an appointment with your doctor.
Most colon cancers are caused by things that doctors don’t know.
Most of the time, colon cancer starts when normal cells in the colon get changes in their DNA. The DNA of a cell has instructions that tell it what to do.
Cells that are healthy grow and divide in a planned way to keep your body working well. But when a cell’s DNA is damaged and it turns into cancer, the cells keep dividing even though they don’t need to. As the cells add up, they form a lump called a tumour.
Over time, the cancer cells can spread into nearby healthy tissue and kill it. And cancerous cells can move to other parts of the body and settle there (metastasis).
Factors that may increase your risk of colon cancer include:
- Older age. Colon cancer can be diagnosed at any age, but a majority of people with colon cancer are older than 50. The rates of colon cancer in people younger than 50 have been increasing, but doctors aren’t sure why.
- African-American race. African-Americans have a greater risk of colon cancer than do people of other races.
- A personal history of colorectal cancer or polyps. If you’ve already had colon cancer or noncancerous colon polyps, you have a greater risk of colon cancer in the future.
- Inflammatory intestinal conditions. Chronic inflammatory diseases of the colon, such as ulcerative colitis and Crohn’s disease, can increase your risk of colon cancer.
- Inherited syndromes that increase colon cancer risk. Some gene mutations passed through generations of your family can increase your risk of colon cancer significantly. Only a small percentage of colon cancers are linked to inherited genes. The most common inherited syndromes that increase colon cancer risk are familial adenomatous polyposis (FAP) and Lynch syndrome, which is also known as hereditary nonpolyposis colorectal cancer (HNPCC).
- Family history of colon cancer. You’re more likely to develop colon cancer if you have a blood relative who has had 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 typical Western diet, which is 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. People who are inactive are more likely to develop colon cancer. Getting regular physical activity may reduce your risk of colon cancer.
- Diabetes. People with diabetes or insulin resistance have an increased risk of colon cancer.
- Obesity. People who are obese have an increased risk of colon cancer and an increased risk of dying of colon cancer when compared with people considered normal weight.
- Smoking. People who smoke may have an increased risk of colon cancer.
- Alcohol. Heavy use of alcohol increases your risk of colon cancer.
- Radiation therapy for cancer. Radiation therapy directed at the abdomen to treat previous cancers increases the risk of colon cancer.
People who have an average risk of colon cancer should think about getting a colon cancer test around age 45, according to doctors. But people with a higher risk, like those who have a history of colon cancer in their family, should think about getting checked sooner.
There are different ways to screen people, and each has its own pros and cons. Talk to your doctor about your options, and you can decide together which tests are right for you.
Lifestyle changes to reduce your risk of colon cancer
You can take steps to reduce your risk of colon cancer by making changes in your everyday life. Take steps to:
- Eat a variety of fruits, vegetables and whole grains. Fruits, vegetables and whole grains contain vitamins, minerals, fiber and antioxidants, which may play a role in cancer prevention. Choose a variety of fruits and vegetables so that you get an array of vitamins and nutrients.
- Drink alcohol in moderation, if at all. If you choose to drink alcohol, limit the amount of alcohol you drink to no more than one drink a day for women and two for men.
- Stop smoking. Talk to your doctor about ways to quit that may work for you.
- Exercise most days of the week. Try to get at least 30 minutes of exercise on most days. If you’ve been inactive, start slowly and build up gradually to 30 minutes. Also, talk to your doctor before starting any exercise program.
- Maintain a healthy weight. If you are at a healthy weight, work to maintain your weight by combining a healthy diet with daily exercise. If you need to lose weight, ask your doctor about healthy ways to achieve your goal. Aim to lose weight slowly by increasing the amount of exercise you get and reducing the number of calories you eat.