Yet it's one of the most treatable cancers there is, even in its later stages.
ABC News' chief health and medical correspondent Dr. Richard Besser held a tweet chat Monday to raise awareness on how to prevent and treat colon and rectal cancer. His special guest was ABC talk show host Katie Couric, whose husband, Jay Monahan, died of the disease in 1998.
CDC director Dr. Tom Frieden and chief medical and scientific officer of the American Cancer Society Dr. Otis Brawley tweeted their thoughts, along with experts from the National Institutes of Health; the Colon Cancer Alliance; Mayo Clinic; New York University Langone Medical Center; and the Dana Farber Cancer Institute.
Here are four things our experts say you must know about keeping your colon happy and healthy:
1. Get Screened
Most colon cancers begin as polyps, lumps growing on the lining of the colon wall that can develop into cancer. Regular screening after the age of 50 is essential for detecting and removing these polyps before they become cancerous.
"Roughly six of 10 deaths from colon cancer could be prevented if everyone age 50+ got screened routinely," Frieden tweeted.
If your test comes back clean, you won't need another one for 10 years. However, if your test shows abnormalities, you should be screened more often.
"Certain types of family history dictate screening at a younger age," Brawley tweeted.
"We think it takes 10 years for a polyp to form and turn into cancer. If we find polyps, we look every three to five years," tweeted Dr. John Kisiel, a gerontologist at the Mayo Clinic.
And colonoscopy isn't the only screening test, according to Besser. You can opt for a sigmoidoscopy, which only examines the bottom of the colon, or a test for blood hidden in the stool instead.
2. Colonoscopies Aren't That Bad
During a colonoscopy, a doctor gently inserts a long, flexible tube with a light and camera on the end into your rectum to scope out signs of cancer. The test itself is no big deal. You're under anesthetic and won't feel a thing.
Prep is another matter. Before the test you need to clean out your colon by drinking copious amounts of a vile-tasting liquid, then retiring to the bathroom for the better part of a day.
Some people find the ordeal daunting, but our chatters said to get over it. And if friends or loved ones resist the idea, Couric said to tell them to do it for the people who love and depend on them.
"Also, if your partner doesn't want to get screened, join them and suggest his and hers colonoscopies!" she tweeted.
3. Don't Die of Embarrassment
"There may be blood in stool, a change in bowel habits, diarrhea or a change in weight," experts from the NIH noted.
Experts from Dana Farber added, "A month or more narrowing of the stools, straining, change in stool shape are all symptoms of bowel problems."
As many of our tweeters noted, people often ignore these symptoms or are too embarrassed to talk to the doctor about them. Here again, our chatters said to get over it.
"Get your butt to the doctor," Couric tweeted - this comment was retweeted more than a dozen times.
As Besser pointed out, however, other than polyps there may be no other symptoms in the early stages of the disease. That's why it's so important to have regular check-ups and get screened on a schedule set by you and your doctor.
4. Know the Risks
Age is an important risk factor. Colon and rectal cancers most often strike people over the age of 50, but the disease can strike at any age. Although anyone can get colorectal cancer, it's deadliest for minorities, because they're less likely to get tested or seek treatment, the experts from the Colon Cancer Alliance said. If someone in your family has had colon cancer, this increases your risk too.
As several tweeters noted, Lynch syndrome - an inherited condition - puts someone at increased risk of colon cancer and other cancers. Doctors estimate that about three out of every 100 colon cancers stem from Lynch syndrome, and the disease often occurs at an earlier age. Lynch syndrome, which is confirmed by a simple blood test, may be a possible diagnosis when there are multiple cases of colorectal cancer on the same side of the family.
The main thing all our tweeters emphasized was that living a colon-healthy lifestyle goes a long way toward prevention of colorectal cancer. Our experts said that a diet high in red meat and low in fiber, smoking, alcohol consumption, a lack of exercise and being overweight or obese add to the risk, although being an exercising vegetarian doesn't completely eliminate your chances of getting the disease.