Healthy Lifestyles and Regular Screenings Would Cut US Colon Cancer Morbidity in Half
Colon cancer has been news recently. This summer, Supreme Court Justice Ruth Bader Ginsburg sought treatment for abdominal distress and was diagnosed with colon cancer. Ginsburg had surgery in September in an attempt to remove the cancer.
Overall, 62% of Americans diagnosed with colon cancer live at least five years post-diagnosis, still approximately 48,000 people die each year from this cancer. Colon cancer is the second leading cause of cancer death in the country.
The good news: More than half of colon cancers can be prevented through lifestyle changes and routine screening.
David Hunter (left) directs the Harvard Center for Cancer Prevention.
Hunter is professor of epidemiology and nutrition. Graham Colditz (right)
is director of education for the center. He is professor of epidemiology
at HSPH and professor of medicine at HMS.
"We've reviewed what is known about colon cancer," said Graham
Colditz, director of education for the Harvard Center of Cancer Prevention.
"And what we found is that this killer is remarkably preventable
through fairly easy changes in diet and physical activity and through
regular screening." Details on prevention measures, in addition to
a discussion of the burden of cancer in the US, are found in the Harvard
Report on Cancer Prevention, Volume 3: Prevention of Colon Cancer in the
United States, printed in the June, 1999, issue of Cancer Causes and
Control.
Colon cancer occurs when cells in the colon, the upper five to six feet of the large intestine, grow out of control. Virtually all colon cancers begin as small non-cancerous tumors called adenomatous polyps. These polyps are relatively common, found in 25% of Americans by age 50, with increasing prevalence as people age. Over the course of time--about 10 to 15 years--some of these polyps may transform and become cancerous.
"The 10- to 15-year timeframe of the adenoma-carcinoma sequence provides us with a valuable opportunity to intervene on risk factors and prevent the development of malignancy," write the authors in the report.
"The number one risk factor for colon cancer is lack of physical activity," said Colditz. "By itself, high levels of physical activity might decrease risk of colon cancer by as much as 50%."
The evaluation screen of the online colon cancer risk index, found at
www.hsph.harvard.edu/colonrisk.
The Harvard Report on Cancer Prevention: Prevention of Colon Cancer
in the United States, can be found online at www.hsph.harvard.edu/Organizations/Canprevent/lead-in.html
While maintaining a high level of physical activity throughout life imparts
the greatest protection, anti-cancer benefits have also been found for
those reporting lower levels of activity, and even for those who only
began to exercise later in life. "The messages here are that, as
far as physical activity is concerned, more is better, some is better
than none, and it's never too late to start," said Colditz.
Several dietary habits that influence people's risk for colon cancer include eating red meat (increases risk); use of multivitamins containing folic acid (reduces risk); and high intake of vegetables (evidence is weak, but a protective effect seems likely).
"In addition to lowering the numbers of colon cancer patients through changes in exercise and eating habits," said Colditz, "we can reduce the suffering and death caused by this disease through screening tests." Two tests have been recommended by the US Preventive Services Task Force and reviewed in the center's report. The tests are the fecal occult blood test and the flexible sigmoidoscopy procedure.
Widespread use of these tests would reduce colon cancer morbidity through two mechanisms: First, they would allow for the detection and removal of precancerous polyps. Second, colon cancer in its early stages is treatable--screening tests would allow physicians to diagnose colon cancer before it is necessarily deadly.
The
risk of dying from colon cancer is reduced by more than a third for people
over age 50 who get screened regularly. This risk reduction may be even
greater for the small percentage of people (estimated to be less than
10% of the population) at high risk due to inheritance of a mutation in
one of the half dozen genes that specify predisposition to colorectal
cancer.
Two other screening tests, colonoscopy and barium enema, are also effective and may be recommended by physicians.
In addition to the annual Harvard Report on Cancer Prevention, the center is also targeting colon cancer reduction through multiple communications efforts. Partnering with the Massachusetts Colorectal Cancer Working Group, the center has developed and distributed to physicians' offices a brochure explaining colon cancer prevention, giving patients valuable information and opening a dialogue about colon cancer between the patient and physician.
The center also takes its message of cancer prevention to the world via the Internet: The Colon Cancer Risk Index is found at www.hsph.harvard.edu/colonrisk/. The index is a pilot project that allows web surfers to answer an interactive questionnaire and discover an approximation of their risk level for colon cancerand, more importantly, what they can do to reduce their risk. In the near future, the risk index will expand to include lung, breast, and prostate cancers.
