Cancers of the lung, breast in women, and prostate in men are the only cancers more common than colorectal cancer. The American Cancer Society (ACS) estimates that about 130,000 people are diagnosed with colorectal cancer each year and about 50,000 people die of this cancer annually in the U.S.

But colorectal cancer can occur at younger ages, and the risk increases gradually throughout life. The ACS recommends regular screenings for colorectal cancer for people at average risk beginning at age 45. Some people at high risk should start even earlier. The screenings can find and remove small precancerous growths called polyps.

At first, colorectal cancer often has few or no symptoms. That’s why it’s so important to get regular screenings. Symptoms can include blood in or on the stool; a change in bowel habits; stools that are narrower than usual; general stomach discomfort; frequent gas or pains; and unexplained weight loss. See your health care provider if you notice any of these symptoms.

The majority of colorectal cancers develop first as polyps. Colorectal polyps are tiny growths inside the colon or rectum that may become cancerous.

Family history does raise your risk, although most people who develop colorectal cancer don't have a strong family history of it. Other risk factors are increased age (it's more common in those 50 and older); a personal history of colorectal polyps or cancer; being African-American; certain diseases of the bowels; obesity; a diet high in red and processed meats; physical inactivity; heavy alcohol use; and smoking.

Several tests are available:

• Fecal occult blood test (FOBT) and fecal immunochemical test (FIT). These check for blood in the stool.
• Stool DNA test. This checks the stool for certain gene changes seen in cancer cells. It also checks for blood in the stool.
• Colonoscopy. This is an exam that looks at the inside of the entire colon and rectum through a flexible, lighted instrument called a colonoscope. The doctor may collect samples of tissue or cells for closer examination.
• Sigmoidoscopy. This is an exam that looks at the inside of the rectum and lower portion of the colon through a lighted tube. The doctor may collect samples of tissue or cells for closer examination.
• Virtual colonoscopy. This is a detailed CT scan of the colon and rectum.

You will need a colonoscopy if you choose any other test and have an abnormal result. Expert groups have different recommendations on when you should get screened. These tests have different ways to get ready for them and might need to be done on different schedules. Talk with your doctor about which tests might be right for you. No matter which test you choose, the most important thing is to get screened.

Researchers have found that people who lead a sedentary lifestyle have a higher risk for colorectal cancer. Getting moderate or vigorous physical activity may lower your risk.

Obesity, like a sedentary lifestyle, appears to increase the risk for colorectal cancer. Getting to and maintaining a healthy weight, by eating a healthy diet and getting regular exercise, may lower your risk for colorectal cancer.