Taking extra folic acid and other B-vitamin supplements may not help protect against colon polyps, according to a U.S. study that contradicts observational studies suggesting people who get more of the vitamins are less likely to get colon cancer.
The study, led by Yiqing Song from Brigham and Women’s Hospital in Boston and published in the Journal of the National Cancer Institute, followed 1,470 women with an average initial age of 62.
The women were randomly assigned to take daily folic acid and vitamins B6 and B12, or a vitamin-free placebo pill, and then followed them to see who developed colon polyps.
All participants had a colonoscopy or sigmoidoscopy to check for colon polyps, which can develop into cancer if not removed, sometime before mid-2007. According to their medical records, 355 had a confirmed polyp.
What is a colon polyp?
A colon polyp is a benign tumor or growth which arises on the inner surface of the colon. Amazingly, from mouth to rectum, the human intestinal tract averages about 30 feet in length. The last six feet is called the colon, or large intestine. Like a piece of pipe, the colon is hollow and the inner surface is normally smooth. For unknown reasons, some individuals grow polyps, or small lumps of tissue, on the inner wall of the colon. There may be single or multiple polyps. The cause is not known, but the incidence of polyps increases with age.
What is a tumor?
All tissues of the body are made up of millions of tiny individual cells. In health, there is a delicate balance. Old cells are constantly dying and are replaced by new healthy cells. If too many new cells form, they create a lump or mass which is called a tumor. Tumors can be benign or malignant. Benign tumors are not cancer. They can usually be removed and, in most cases, they do not grow back. Cells from benign tumors do not spread to other parts of the body. Most important, benign tumors are rarely a threat to life. Malignant tumors are cancer. Cells in these tumors are abnormal and they continue to divide uncontrollably. Without treatment, they can invade and spread to nearby tissues and organs.
What does a polyp look like?
Colon polyps are found in one of two shapes. Polyps on stems or stalks look like mushrooms and are called pedunculated. When they grow directly onto the inner wall of the colon like spilled paint, they are called sessile and are much more difficult to remove.
Why remove polyps if they are benign?
Colon polyps are important, since some may turn into colon cancer over time. While not every colon polyp turns to cancer, it is felt that almost every colon cancer begins as a small non-cancerous polyp. Fortunately, during colonoscopy. these polyps can be identified and removed or destroyed - thus preventing a possible colon cancer. If a polyp is large enough, tissue can be retrieved and sent for biopsy to determine the exact type of polyp.
What are the types of colon polyps?
There are basically 4 types of polyps that commonly occur within the colon:
1. Inflammatory - Most often found in patients with ulcerative colitis or Crohn’s disease. Often called “pseudopolyps” (false polyps), they are not true polyps, but just a reaction to chronic inflammation of the colon wall. They are not the type that turns to cancer. They are usually biopsied to verify type.
2. Hyperplastic - A common type of polyp which is usually very small and found in the rectum. They are considered to be low risk for cancer.
3. Tubular adenoma or adenomatous polyp - This is the most common type of polyp and the one referred to most often when a doctor speaks of colon polyps. About 70% of polyps removed are of this type. Adenomas carry a definite cancer risk which rises as the polyp grows larger. Adenomatous polyps usually cause no symptoms, but if detected early they can be removed during colonoscopy before any cancer cells form. The good news is that polyps grow slowly and may take years to turn into cancer. Patients with a history of adenomatous polyps must be periodically reexamined.
4. Villous adenoma or tubulovillous adenoma- About 15% of polyps removed are of this type. This is a much more serious type of polyp that has a very high cancer risk as it grows larger. Often they are larger and sessile and not on a stem making removal more difficult. Smaller ones can be removed in piecemeal fashion - sometimes over several colonoscopies. Larger sessile villous adenomas may require surgery for complete removal. Follow up depends on size and completeness of removal.
Polyp risk was not related to treatment group, with 24.3 percent of women taking the vitamins developing polyps compared to 24.0 percent of those on placebo pills. The lack of benefit remained after the researchers accounted for women’s weight as well as smoking, alcohol and exercise.
“Where we really are is a kind of interesting impasse,” said John Baron, an epidemiologist from the Geisel School of Medicine at Dartmouth University in Lebanon, New Hampshire, who was not involved in the study.
Polyps don’t always become cancerous, but your risk of developing colon cancer increases with the number and size of polyps you have. Approximately one percent of polyps with a diameter less than a centimeter are cancerous. If you have one little polyp that size, the American Cancer Society (ACS) recommends that the doctor remove it and that you receive another colonoscopy three to six years later. (Without any polyps, the due date would have been ten years later.)
If you have more than one polyp or the polyp is bigger than a centimeter, you’re considered at even higher risk for colon cancer. After your polyps are removed, you’ll probably be asked to get another colonoscopy in three years. The doctor may also test the polyp since up to 50% of polyps greater than two centimeters (about the diameter of a nickel) are cancerous.
Relatives with Polyps
When it comes to polyps and colon cancer risk, family history is important. It’s probably not the most comfortable conversation to have, but you should find out if your parents, siblings, or children have ever had any colon polyps. If they have, you’re not in the average-risk category for colon cancer anymore.
If two or more first-degree relatives have had polyps, the ACS recommends that you receive your first colonoscopy at age 40 or ten years before the age when your relative’s polyp was found, whichever is earlier. Both of my parents have had polyps, so I’ll be getting a colonoscopy when I’m 40 instead of when I’m 50.
Another family scenario that would increase your risk is if one first-degree relative had a polyp before age 60. So, one parent with a polyp or one sibling with a polyp. The same higher-risk recommendations apply. So if your brother had a polyp removed when he was 45, the ACS says you should get a colonoscopy when you’re 35.
“The observational data continually show an inverse association between measures of folic acid, that is diet or blood level, and the risk of colorectal cancer. The clinical trial data such as we have… suggest no benefit overall.”