A Colon Polyp Snared and Gone

We thought it was true . . . and now research comes along with evidence.

Colonoscopy reduces death from colorectal cancer.

In a follow-up analysis from the National Polyp Study, people who had adenomas — the risky kind of polyps — removed during the study were much less likely to die from colon or rectal cancer than  the general US population.  In fact, removing adenomas cut the death rate from colorectal cancer in half.

We knew that colonoscopies find and remove precancerous polyps and reduce the number of new colorectal cancers, but this is the first study to actually link colonoscopy to cutting back death from colorectal cancer.

There was good news in the study for people who didn’t have adenomas too. They had a very low risk of colorectal cancer death. Only one person out of nearly 800 with no adenomas found at the initial exam  died of colorectal cancer.

Between 1980 and 1990, the National Polyp Study (NPS) enrolled patients  who were having a colonoscopy to rule out colorectal cancer due to symptoms or positive finding on another test.  All polyps were removed during the exam. Patients with adenomas had another colonoscopy 1 or 3 years later and again at 6 years. Patients with no polyps or only benign hyperplastic ones had no further testing.

For this long-term follow-up study, Ann Zauber, PhD, and her team used the National Death Index to find those patients in the NPS who died from colorectal cancer. The researchers used the National Cancer Institute’s Surveillance, Epidemiology, and End Results (SEER) registry to figure out how many colorectal cancers could be expected in a group of people with the same age, race, and sex of the NPS participants.

Comparing  2602 NPS adenoma patients to what was expected in the general population there were:

• Overall, 12 deaths in the NPS group compared to an expected 25.4.
• In less than 10 years 4 NPS deaths compared to an expected 9.1.
• For more than 10 years 8 NPS deaths compared to 16.3

In the follow-up study, 2602 patients had adenomas found during their initial colonoscopy, another 773 didn’t.

About a third of the people in the control group did have polyps. But they were the safer hyperplastic type. Only one person in that group of 773 died of colorectal cancer. She died about 8 years after her initial colonoscopy.

Ann Zauber PhD and her team concluded,

These findings support the hypothesis that colonoscopic removal of adenomatous polyps prevents death from colorectal cancer.

Dr. Zauber also wrote,

A demonstrated reduction in mortality with colonoscopic polypectomy is a critical prerequisite for continued recommendations of screening colonoscopy in clinical practice while we wait for the results of randomized, controlled trials of screening colonoscopy.

SOURCE: Zauber et al, New England Journal of Medicine, February 23, 2012.

 What This Means for Patients

Advocates can confidently say that colonoscopy saves lives. Not only does it prevent colorectal cancer from ever happening, it cuts deaths in half.

However, deaths were not zero. Patients who have had adenomas removed during a colonoscopy need to remain aware of the symptoms of colorectal cancer and have them evaluated with another colonoscopy if they occur.

It is also important to remember that the National Polyp Study involved high quality colonoscopies. The gastroenterologists who performed them were experts and all cases included in the study reached the top of the colon.

Taking either high or low dose aspirin reduces the chances the people with colorectal polyps (adenomas) will get more.

A combined analysis of three randomized controlled trials that compared taking aspirin to a placebo after adenomas were removed found that people who took a daily low dose or baby aspirin had almost a 20 percent lower chance of another adenoma during their next colonoscopy.  High-dose or regular adult strength aspirin reduced risk of polyp recurrence by about 15 percent.

Any aspirin reduced the risk of advanced adenomas by more than 35 percent.

Advanced adenomas include polyps over 10 millimeters or polyps that are especially risky for developing into cancer including those with significant villous features,high-grade dysplasia, or early invasive cancer.

In the three studies, over 2300 people with polyps on their initial colonoscopy were randomly assigned to aspirin or a placebo in the three studies, and 2,175 had a second colonoscopy to look for new polyps.

F. Gao and colleagues concluded,

This meta-analysis suggests that aspirin prevents recurrent colorectal adenomas among patients with a history of colorectal adenomas.

SOURCE:  Gao et al., Colorectal Disease, Volume 11, Number 9, November, 2009.

Results from two colonoscopies three years apart gave better information about whether a high-risk polyp would be found on a third exam than results from the second test alone.

Even if a second colonoscopy, done three years after the first, showed no adenomas at all, 8 in 100 study participants with high-risk polyps on their first exam had developed a high-risk polyp by six years when they had a third colonoscopy.

In the Aspirin/Folate Colorectal Polyp Prevention Study, 564 participants had three colonoscopies:  one at the beginning of the study, one three years later, and a third three years after that.  All of the people in the study had at least one polyp at the beginning of the study, but not all had polyps considered to be high-risk.

High risk patients had an adenoma 1 centimeter or larger, three or more adenomas, or a polyp with advanced pre-cancerous changes.

• Patients whose first colonoscopy had high risk polyps but had no adenomas at all on a second study, had a 7.7 percent chance that their third exam would reveal a high-risk polyp.
• Those with initial high-risk adenomas and a low-risk second exam had a 1 in 10 chance of a high-risk third exam.
• Those who were low-risk on both a first and second colonoscopy had a less than 5 percent chance of having a high-risk polyp found during the third exam.
• Patients were were high risk at their second exam had a 1 in 5 (20 percent) chance that an advanced polyp would be found during their third test.  For these patients, it made no difference whether they were high or low risk with their first colonoscopy.

Douglas J. Robertson, MD, MPH, and colleagues concluded,

Information from 2 previous examinations may help identify low-risk populations that benefit little from intense surveillance. Surveillance guidelines might be tailored in selected patients to use information from 2 previous examinations, not just the most recent one.

SOURCE: Robertson et al., Annals of Internal Medicine, Volume 151, Issue 2, July 21, 2009.

Both the level of vitamin D in the blood and intake of vitamin D-rich foods decrease the risk of colorectal polyps in a number of studies.

Analyzing published studies of blood levels of vitamin D, researchers found a 30 percent decrease in the risk of adenomas among people with the most circulating vitamin D compared to those with the least.  The highest vitamin D intake decreased adenomatous polyp risk by 11 percent.

In addition, there appeared to be an even stronger relationship between both blood levels and vitamin D intake for advanced adenomas, with the highest risk of cancer.  Higher blood levels decreased risk of advanced adenomas by 46 percent, greater intake of vitamin D by 23 percent.

Melissa Wei and her colleagues concluded,

Both circulating 25(OH)D and vitamin D intake were inversely associated with colorectal adenoma incidence and recurrent adenomas. These results further support a role of vitamin D in prevention of colorectal adenoma incidence and recurrence.

SOURCE: Wei et al., Cancer Epidemiology, Biomarkers, and Prevention, Volume 17, Number 11, November 2008.