20 Things You Didn’t Know About Colon Cancer

What is the best prevention against colon cancer?

Reviewed by Davia Sills

Key points

• There has been a recent increase of colon cancer in people between the ages of 45 and 50.
• The 5-year survival rate is 91.1 percent for localized lesions, but only 15.7 percent for distant metastasis.
• The risk of colon cancer increases with obesity, diabetes, and a diet high in red meats and processed meats.
• A new assay called liquid biopsy can detect circulating tumor DNA in the blood.

When I ask people over the age of 45 if they have had a screening colonoscopy for colon cancer, a lot of them answer “no.” And when I ask them if they plan on getting a colonoscopy in the next few months or years, many of them say that they don’t really know because they think that colorectal cancer won’t affect them, so they don’t worry about it.

20 things you probably don’t know about colon cancer

But if you are 45 or older, you should really worry about colon cancer because there are many facts you probably don’t know about it.

1. Your lifetime risk of developing colon cancer is four percent, which means that if 50 people read this article, at least two will develop colon cancer in their lifetime, according to the Surveillance Epidemiology and End Results (SEER) statistics [1].
2. Colorectal cancer is the third most common type of cancer in the U.S. for men, the fourth most common type of cancer for women, and the second most common cause of cancer deaths (after lung cancer) [2].
3. There has been a recent increase in colon cancer in people between the ages of 45 and 50.
4. But in general, colorectal cancer is most frequently diagnosed among people aged 55-74, and the median age for colorectal cancer diagnosis is 66.
5. Forty-five is an important age to remember: In 1997, the American Gastroenterological Association published guidelines recommending colon cancer screening for all average-risk adults starting at age 50. Fast-forward to today (since 2021), screening now begins at age 45.
6. According to the American Cancer Society, the risk of colon cancer increases with a diet high in red meats (such as beef, pork, or lamb) and processed meats (like hot dogs and some lunch meats). Also, frying, broiling, or grilling meats at very high temperatures creates chemicals that might raise cancer risk. Having a low blood level of vitamin D may also increase that risk. Obesity, diabetes, smoking, moderate to heavy alcohol use, and a family history of colon cancer also increase that risk [3].
7. The number of estimated new cases of colon cancer in the U.S. in 2024 is 152,810, and the number of estimated deaths from colon cancer in the U.S. in 2024 is 53,010, according to SEER statistics.
8. If you have a first-degree relative with colon cancer, start screening for colon cancer at age 40 or 10 years before the age when your first-degree relative was diagnosed.
9. A study that did 200 colonoscopies on asymptomatic siblings of people with advanced adenoma, which is a lesion ready to turn into cancer, found that 12 percent of those asymptomatic siblings also had advanced adenoma [4].
10. The 5-year survival rate is 91.1 percent if the cancer is localized, but only 15.7 percent if there are distant metastasis according to SEER. So, the earlier the detection, the better.
11. It takes an average of 7 to 10 years for a polyp to develop into cancer [5]. First, abnormal cells appear in a small part of the polyp; then, little by little, they invade the whole polyp; then, they invade blood vessels and structures next to it; then they metastasize to the lymph nodes, liver, lungs, brain, and other organs.
12. The gold standard test for colon cancer is a colonoscopy, which is the only test that allows both diagnosis and treatment in the same procedure. The diagnosis is done by looking around in the colon with a scope, then biopsying abnormal lesions. The treatment is done by resecting the suspected lesion(s) during the colonoscopy. But colonoscopies need to be done by a well-trained gastroenterologist who has a good adenoma detection rate. If the gastroenterologist goes too fast, he or she could miss lesions. It is also important that the prep is adequate. If there are stools left in the colon, the gastroenterologist will not see the colon mucosa well and could miss lesions. The prep is on you, the patient. The training is on the physician.
13. Cancers detected in the right ascending colon tend to have a worse prognosis than cancer in the left descending colon. It seems that right colon lesions invade vessels earlier and are detected later [6].
14. Depending on the number, size, and type of polyps found, a repeat colonoscopy will be recommended, varying from 1 year later (if more than 10 adenoma-type polyps are found) to 10 years later (if the colonoscopy is normal).
15. There are other tests if you don’t want a colonoscopy. You could do a CT colonography, which is a radiological test, but it requires the same prep as a colonoscopy: It will miss flat lesions, and if it detects anything abnormal, you will still need a colonoscopy for biopsy and treatment.
16. You could also simply do a sigmoidoscopy, but that will only explore the left part of your colon. What if you have a cancerous lesion on the right part of your colon?
17. FOBT (fecal occult blood test) can detect hidden blood in your stools (which can indicate colon cancer) via peroxidase activity. Because of the way it works, it can have false positives if you eat certain foods. So, a few days before your stool test, stay away from turnips and broccoli, which contain peroxidases; stay away from red meat, which contains heme; and avoid citrus fruits and vitamin C, which interfere with peroxidase tests. FOBT is done once a year. You can buy the kit over the counter.
18. FIT (fecal immunochemical test) is a different way to detect blood in your stools. You don’t need to worry about diet, medication, or supplements because FITs detect human blood by antibodies. But because human blood is digested by your upper GI, FITs will not detect blood coming from your esophagus, stomach, or duodenum. The test will only detect undigested blood coming from your intestine. You can buy the kit over the counter and do the test once a year.
19. The Cologuard Test is an assay for several mutated genes associated with colon cancer as well as a FIT. If negative, it is recommended to repeat it three years later. The medical community is not sure yet if it is better and more cost-effective than a simple yearly FIT.
20. A new blood assay can detect circulating tumor DNA. This technique, called liquid biopsy, is currently used in some facilities to detect people at high risk of recurrence of cancer after treatment [7], and in the future, when this new blood assay becomes more affordable, it could hopefully be widely used to detect colon cancer [8].

Conclusion

If you are 45 or older, scheduling an appointment with a gastroenterologist for a colonoscopy could save your life. If you wait until you are obstructed and have liver, lung, or brain metastasis, it might be too late, and you will need surgery, chemotherapy, and radiation therapy. These treatments are long, complicated, and painful.

But if you want a simple and fast solution, have regular colonoscopies: If a suspicious lesion is found, immediately removing it could be the end of the problem. Also, watch your weight and don’t eat red meat or processed meats too often because prevention of colon cancer is key.

As Albert Einstein said: “Intellectuals solve problems, geniuses prevent them.”

Copyright 2024 @ Chris Gilbert, M.D., Ph.D.