Colorectal cancer strikes down thousands of Americans every year. Fortunately, there’s a way to prevent this disease and these deaths.
About 40 percent of all colorectal cancers could possibly be prevented with regular colonoscopy screening, according to a new long-term study.
Colonoscopy, which examines the entire inside of the colon, was associated with lower mortality from proximal colon cancer. Both colonoscopy and sigmoidoscopy were associated with lower mortality from colorectal cancer.
Another recent study, published in the same journal, found that a non-invasive method of colorectal cancer screening — called a fecal occult-blood test — was also effective in reducing colorectal cancer deaths.
Shuji Ogino, MD, associate professor in the Department of Epidemiology at the Harvard School of Public Health, and colleagues conducted the study to determine if colonoscopies reduced colorectal cancer incidence and mortality.
Colorectal cancer will be diagnosed in some 143,000 Americans and kill 51,000 men and women in the US this year. It's the second leading cause of cancer-related death in the US.
For this study, the researchers examined data from participants in two long-term studies — the Nurses' Health Study and the Health Professionals Follow-up Study.
Individuals in both studies completed surveys every two years between 1988 and 2008. Study members were asked if they had undergone either a sigmoidoscopy or colonoscopy and the reason for the screening.
Among the group of nearly 89,000 study participants, 1,815 cases of colorectal cancer were diagnosed and 474 deaths resulted from the disease.
Sigmoidoscopy examines the lower or distal part of the colon, while colonoscopies examine both the distal and proximal, the upper part of the colon.
The researchers found that both tests reduced the risks of developing and dying from colorectal cancer. However, only colonoscopy was effective in protecting against cancers in the upper part of the colon.
The protective effects of colonoscopy were not as great for the upper part of the colon as they were for the lower colon. The researchers suggested this may be because tumors in this area of the colon have different molecular and biological properties than tumors in the lower colon.
For people without increased risk of colorectal cancer such as a family history of the disease, colonoscopies are recommended to start at age 50 and be repeated every 10 years as long as nothing suspicious is found. If polyps (precancerous lesions) are found during the exam, a colonoscopy should be repeated every five years.
Sigmoidoscopies should be repeated every five years, according to current recommendations.
“We estimated that 40 percent of colorectal cancers (including 61 percent of distal colorectal cancers and 22 percent of proximal colon cancers) that developed during follow-up would have been prevented if all the participants in our study had undergone colonoscopy,” the authors wrote.
Based on the study findings, the researchers also concluded the following:
- Sigmoidoscopy probably is not effective in preventing or reducing deaths from upper colon cancers.
- Someone who has a clean colonoscopy may be protected against colorectal cancer for up to 15 years, reinforcing the benefit of colonoscopy every 10 years.
- Tumors found within five years of a colonoscopy tend to have different molecular structures than those found at longer intervals.
Eric Haas, MD, colorectal surgeon at Houston Methodist Center for Restorative Pelvic Medicine, told dailyRx News, "Screening tools such as colonoscopy and sigmoidoscopy are again proven to be invaluable instruments for the early detection of colorectal cancer.
"New technologies including genetic and molecular testing are being evaluated to further help identify high-risk patients who may benefit from increased frequency of screening due to elevated risk of developing colorectal cancer," said Dr. Haas, who was not involved in this study.
Results from this study were published September 18 in The New England Journal of Medicine.
Support for the research came from the National Institutes of Health, the Bennett Family Foundation and the Entertainment Industry Foundation through the National Colorectal Cancer Research Alliance.