The only way to definitively know if you have colon cancer is to be evaluated for it. There are many different ways of screening for colon cancer. Colonoscopy is considered the standard because it not only can detect cancer and precancerous polyps, it can also serve as a way to biopsy the abnormal tissue for diagnosis. In some cases, the doctor can completely remove the polyps before they become cancer. You should have a discussion with your physician to see if and when you should undergo a colonoscopy.

Oftentimes, colon cancer or precancerous polyps do not produce any symptoms. In other words, there is nothing that suggests they are there. That is one of the reasons colonoscopy is so important as a screening tool. Sometimes, patients will have symptoms that could be caused by colon cancer, such as a change in bowel habits (for example, new onset of constipation or need to strain, diarrhea, and/or thinning of the caliber of stools), crampy abdominal pain, or bleeding from the anus with or without bowel movements. These symptoms should be evaluated by a physician who can determine if you need a colonoscopy.

Answered by Charis Eng, MD, PhD. Dr. Eng is Department Chair of the Genomic Medicine Institute and American Cancer Society Professor at Cleveland Clinic. She is the founding director and attending clinical cancer geneticist of the Institute’s clinical component, the Center for Personalized Genetic Healthcare.