Medically reviewed by Robert (Dobbin) T.P. Chow, MD, MBA.
Colon cancer is the uncontrolled growth of cells in the colon, which is also known as the large intestine. You may also hear the term colorectal cancer, which refers to cancer in the rectum (the last part of the large intestine) and colon.
The disease often starts as tiny polyps, which are abnormal growths of tissue. Polyps are not cancerous at first, but they can become cancerous over time. You can have these polyps for years without having any symptoms. Knowing what increases your risk, recognizing warning symptoms and staying on schedule with screening can help you detect colon cancer early, when it’s most treatable.
What Is the Main Cause of Colon Cancer?
There’s no single cause of colon cancer. However, experts know that certain lifestyle factors, like your diet and activity level, can make you more likely to develop this type of cancer.
Colon Cancer Risk Factors
Some colon cancer risk factors are controllable, meaning your risk can get higher or lower depending on your lifestyle and habits. Other risk factors, such as your age, are beyond your control.
Controllable Risk Factors
- Consuming a diet high in fat, red meat and processed meat
- Heavy alcohol use
- Obesity
- Sedentary lifestyle
- Smoking
Uncontrollable Risk Factors
- Inflammatory bowel disease (IBD): Conditions such as ulcerative colitis and Crohn’s disease increase risk, especially when the disease has been present for many years.
- Your race: African American individuals and those of Ashkenazi Jewish descent are at higher risk.
- Your age: The risk increases as you get older. Recent guidelines recommend that most people begin screening at age 45, down from age 50, because colorectal cancer rates among younger people have been rising.
- Your family history: Having a parent, sibling or child with colorectal cancer or precancerous polyps makes you more susceptible to the disease, especially if the relative was diagnosed before age 50.
- Your genetics: Genetic conditions like Lynch syndrome and familial adenomatous polyposis also increase the likelihood of getting colon cancer.
What Are the Early Warning Signs of Colon Cancer?
In its early stages, colon cancer may not have any symptoms. The condition can develop and go undetected for years. It’s essential to know what to look for so you can report these symptoms to your doctor when you first notice them. These symptoms may resemble those of other conditions, such as irritable bowel syndrome. If any of the following symptoms last for more than a few days, talk with your doctor to get an accurate diagnosis.
Possible symptoms include:
- Abdominal pain, cramps, gas or bloating
- Blood in the stool or rectal bleeding, which can show up as bright red blood or make stool appear dark or black
- Change in bowel habits, which can include diarrhea, constipation or a feeling that bowel movements are not complete
- Fatigue, or feeling tired more often than usual
- Narrowing of the stool or a change in its shape
- Unintended weight loss
- Weakness
When to Get a Colon Cancer Screening
The best time to get a screening depends on your age and other factors, like your family history. Getting screened for colon cancer is important, especially as you get older. Your risk of developing the disease goes up after age 45, which is why doctors recommend getting your first colonoscopy around this time. If you have a higher risk for other reasons, your doctor might suggest getting checked even sooner.
Screening tests are so important because they can find cancer early, when it’s much easier to treat and the chances of survival are higher. Unfortunately, many people don’t get screened when they should. According to the Centers for Disease Control and Prevention, only half of adults ages 50 to 54 are up-to-date with their screenings for colon and rectal cancer.
Colonoscopy
A colonoscopy is a procedure that allows doctors to examine the inside of the colon and rectum using a long flexible tube equipped with a camera. It is a highly effective screening tool for detecting colon cancer, as it can identify precancerous polyps and early-stage cancers. If such lesions are identified, a biopsy can be performed via colonoscopy. A biopsy is a small sample of your colon lining. Looking at the biopsy sample under the microscope will reveal whether colon cancer is present. Therefore, colonoscopies are generally considered the gold standard for detecting colon cancer.
Stool Tests
A fecal immunochemical test with DNA analysis (FIT-DNA) is an at-home test for colorectal cancer. You collect a stool sample, and a lab checks for two things: hidden blood and abnormal DNA that could come from cancer or growths called polyps. It’s a simple way to screen for the disease. If the stool sample contains colon cancer DNA, then a colonoscopy is required to find the location and extent of the cancer.
In Summary
Colon cancer is a common disease, but it’s also one of the most treatable types of cancer. Early detection is crucial because treatment is more successful when cancer is in its early stages. You can also take steps to lower your risk by focusing on factors you can control, like scheduling a screening and eating a healthier diet.
When it comes to colon cancer:
- Understand your risk factors. Find out about your family history and whether you have other factors that increase your risk.
- Get screened when your doctor recommends it.
- Adopt a healthy lifestyle that includes a balanced diet, regular activity, limited alcohol and no tobacco smoking.
Watch an Interview
Colon Cancer 101: Tests, Truths and Timing
There’s more than one way to screen for colon cancer—do you know your options? In this episode, three medical experts from the University of Maryland Midtown Health Center will walk you through the latest in screening options—from colonoscopies to FIT-DNA tests—and how to choose what’s right for you. Learn the facts, understand your risks and hear real stories of lives saved by timely screening. Featured Speakers: Jeff Gerbino, MD, Greg Lalonde, MD and Dobbin Chow, MD from University of Maryland Medical Center Midtown Primary Care.