Switching from a “Western” diet with lots of fat and meat to a fiber-rich diet for just two weeks makes conditions in the large intestine less favorable to the development of colon cancer. The opposite switch may promote the formation of cancer. That’s the conclusion from a small but elegant study done in urban Pittsburgh and rural KwaZulu-Natal, South Africa. In the study, 20 volunteers from each area switched diets. For two weeks, the Americans ate a traditional high-fiber African diet rich in fruits, vegetables, nuts, and beans, while the Africans ate a Western diet with more fat, protein, and meat. In just two weeks, significant changes occurred in the lining of the colon and in its chemical and bacterial make-up in both groups, but in different directions. Those following the African diet showed improvements in colon health likely to protect against colon cancer, while those following the Western diet showed changes that could lead to colon cancer.
Looking for ways to ward off colorectal cancer? According to a new study, a pescovegetarian diet — that’s a vegetarian diet that includes fish — was linked to a 43% reduction in the risk of developing colorectal cancer. The study, published in JAMA Internal Medicine, adds more support to the notion that something in red meat, or the way it is cooked, encourages the growth of colorectal cancer. It’s also possible that eating more plant foods provides extra beneficial nutrients such as folate, calcium, and fiber that may protect against colorectal cancer. Fish contain healthful omega-3 fats and vitamin D. Another good strategy for preventing harm from colorectal cancer, the second leading cause of cancer death in the United States? Have colonoscopies as needed.
Some good news on the cancer front: between 2000 and 2010, rates of colorectal cancer in American adults fell by about one-third. That decline mirrored a sharp rise in colorectal cancer testing during the same period. American Cancer Society researchers found that the drop in colorectal cancer rates was highest among Americans aged 65 years and older. Cases fell 3.6% a year from 2001 to 2008, then dropped even more by 7.2% a year from 2008 to 2010. But the researchers saw a troubling trend in younger adults: an increase in colorectal cancer of 1.1% a year among people under age 50. Rising obesity rates may be to blame. The researchers attribute the decline in colorectal cancer to early testing for the disease. Despite the optimistic findings, colorectal cancer is still a scourge. In the U.S. this year, an estimated 72,000 men and 65,000 women will be diagnosed with colorectal cancer; 26,000 men and 24,000 women will die of it.
Checking seemingly healthy people for cancer—what doctors call screening—seems like a simple process: Perform a test and either find cancer early and cure it or don’t find it and breathe easy. It works for colon, breast, and cervical cancers, but not for others. For colon cancer, there are several effective screening tests: colonoscopy, sigmoidoscopy, and stool testing. Two new studies in yesterday’s New England Journal of Medicine help further quantify their benefits. In the studies, all three types of test reduced the risk of developing or dying from colon cancer. Colonoscopy worked best, followed by sigmoidoscopy and then stool testing. The biggest challenge for colon cancer screening is getting people to have the available tests. About 50,000 Americans die of colon cancer each year—many of these can be prevented with early screening.
Aspirin has many uses, from easing a headache or cooling a fever to preventing heart attacks and the most common kind of stroke. It may be time to add “preventing colorectal cancer” to the list. New results from the Women’s Health Study, a clinical trial that evaluated the benefits and risks of low-dose aspirin and vitamin E among nearly 40,000 women, show that aspirin reduces the risk of developing colorectal cancer by 20%. The effect isn’t immediate, but instead takes ten to 20 years to be seen. Aspirin isn’t without its drawbacks, including gastrointestinal bleeding and ulcer formation. Both occurred slightly more often among women taking aspirin. Although the Women’s Health Study results sound promising, don’t go reaching for the aspirin bottle just yet. Taking aspirin—and any other drug—is really a balancing act between benefits and risks.
Back in 2009, Dr. Andrew T. Chan and his colleagues at Harvard-affiliated Massachusetts General Hospital found that people diagnosed with colorectal cancer who took aspirin on a regular basis tended to live longer than those who didn’t take aspirin. Aspirin worked only for some people, though, so Chan and a larger team of researchers set out to learn why. Their latest work, published in the New England Journal of Medicine, indicates that people with colorectal cancer who have a mutation in a gene called PIK3CA are most likely to benefit from aspirin. (About 15% to 20% of people with colorectal cancer have this gene mutation.) The mutation permits colon cancer cells to thrive. Aspirin blocks this action. If confirmed, this work could lead to routine genetic testing for people with this common cancer, and aspirin therapy for those with the PIK3CA mutation.
An experimental approach to virtual colonoscopy could eliminate the unpleasant day-before bowel prep that keeps many people from having this potentially life-saving test. Virtual colonoscopy uses computed tomography (CT) scanning with X-rays, instead of a scope, to check the colon for cancers and precancerous polyps. Earlier version have required bowel cleaning, just like regular colonoscopy. A Harvard-based team led by Dr. Michael Zalis uses sophisticated computer software to make stool in the colon disappear. It’s a little like Photoshopping blemishes from still photos. “Laxative-free CT colonography has the potential to reach some of the unscreened population and save lives,” says Dr. Zalis, an associate professor of radiology at MGH and director of CT colonography at MGH Imaging.