March 10, 2011 — The majority of colorectal cancer could be prevented by applying existing knowledge about cancer prevention and by increasing the use of established screening tests, according to the American Cancer Society (ACS).
"The value of early detection has become a topic of wide debate for some cancers," said Edward Partridge, MD, national volunteer president of the ACS. For example, debates have raged about prostate-specific antigen testing for prostate cancer and mammography for breast cancer, as previously reported by Medscape Medical News.
"But for colorectal cancer there should be no debate," Dr. Partridge said in a statement. "Screening for colon cancer saves lives."
However, despite the evidence supporting the effectiveness of colorectal cancer screening and the availability of various screening tests, only about half the American population 50 years or older is current for recommended testing, the ACS points out.
"The American Cancer Society has identified colorectal cancer as a major priority because of the enormous potential to prevent disease, diminish suffering, and save lives," Dr. Partridge said.
The ACS has just released a new report, Colorectal Cancer Facts & Figures 2011-2013, to coincide with National Colon Cancer Awareness Month in the United States. Throughout March, and throughout the year, the ACS encourages colorectal cancer screening for people 50 years and older.
The ACS also encourages physicians to proactively recommend regular screening and, to that end, it highlights the online resource How to Increase Colorectal Cancer Screening Rates in Practice: A Primary Care Clinician's Evidence-Based Toolbox and Guide.
More Than Half the Deaths Could Be Avoided
The ACS report estimates that during the course of this year, some 141,210 new cases of colorectal cancer will be diagnosed (about 72% in the colon and 28% in the rectum). It also predicts about 49,380 deaths from the disease during 2011, and says that more than half of these lives could have been saved with recommended screening.
In addition, about one quarter of cases of colorectal cancer could be prevented by a healthy lifestyle, the report notes. This involves maintaining a healthy abdominal weight, being physically active at least 30 minutes per day, eating a healthy diet, not smoking, and not drinking excessive amounts of alcohol.
However, the key message for people 50 years and older is that "screening is the most important step you can take to help protect yourself from colon cancer," the report states.
Screening Options
There are several recommended options for colorectal cancer screening; any of these is useful in average-risk adults, the report notes.
Options for Screening for Colorectal Cancer
| Test | Test Interval |
| Flexible sigmoidoscopy | 5 years |
| Colonoscopy | 10 years |
| Double-contrast barium enema | 5 years |
| Computed tomography colonography (virtual colonoscopy) | 5 years |
| Fecal occult blood test | 1 year |
| Stool DNA test | undetermined |
Of the available options, structural exams (flexible sigmoidoscopy, colonoscopy, double-contrast barium enema, virtual colonoscopy) are preferable to stool tests (fecal occult blood test, stool DNA test) because they are likely to detect precancerous polyps and growths in addition to early cancer.
This is the recommendation of consensus guidelines for colorectal cancer screening issued in 2008 by the American Cancer Society in association with the US Multi-Society Task Force (which includes the American College of Gastroenterology and the American College of Physicians) and the American College of Radiology (CA Cancer J Clin. 2008;58:130-160).
Colonoscopy has the potential to prevent about 65% of colorectal cancer cases, the report notes, whereas sigmoidoscopy is associated with a 60% to 80% reduction in colorectal cancer mortality for the area of the colon within its reach.
Regular use of fecal occult blood tests reduces the risk for death from colorectal cancer by about 15% to 33%. However, its effectiveness is dependent on repeat screenings over time, the report notes, and a recent study has shown that the majority of people who choose this option fail to adhere to a regular testing schedule.
Guaiac-based "toilet-bowl tests" that are sold over the counter are not recommended by the ACS or any other major medical organization. These tests, often promoted as a type of fecal occult blood test, consist of strips of paper that are dropped into the toilet water containing the stool, but these tests have not been evaluated in rigorous clinical studies, the report notes.
Screening Shows Modest Increase
Screening for colorectal cancer has been increasing modestly since 2000, owing exclusively to an increase in endoscopy (both sigmoidoscopy and colonoscopy), the report notes.
Nevertheless, data for 2008 show that only 50% of the adult population 50 years and older reported having had an endoscopy and only 10% reported having a fecal occult blood test within the recommended time intervals.
Screening prevalence is lower among people 50 to 64 years than among those 65 years and older. This is especially low among those who are nonwhite, who have fewer years of education, who lack health insurance, and who are recent immigrants, the report notes.
Rates Declining in Recent Years
The incidence of colorectal cancer has been declining in the United States since the mid-1980s, and this decline has accelerated in recent years. Since 1998, incidence rates have fallen by 3% per year in men and by 2.3% per year in women.
The acceleration in this decline in the past decade has been largely attributed to colorectal cancer screening and the detection and removal of precancerous polyps, the report notes.
However, although the incidence rates have been declining in adults 50 years and older, there has been an increase in the incidence of colorectal cancer among adults younger than 50 years. This increase appears to be confined to cancers of the distal colon and rectum. "The reasons for this increase are unknown, but may reflect increasing trends in obesity and/or unfavorable dietary patterns in children and young adults," according to the report.
As with incidence rates, deaths from colorectal cancer have been decreasing in the United States, since around 1950 in women and around 1980 in men. Since 1998, deaths from colorectal cancer have been decreasing by 2.8% per year in men and by 2.6% per year in women.
However, over the past 3 decades, there has been an increasing divergence of mortality trends between whites and blacks. Steep declines in mortality, largely the result of substantial improvements in the early detection and treatment of colorectal cancer, began in whites in the early 1980s, but were not see in blacks until the late 1990s. As a result, colorectal mortality rates have been substantially higher among blacks than among whites (they were 44% higher in 2007).
Blacks are less likely than whites to receive most appropriate surgery, adjuvant chemotherapy, and radiation treatments after a cancer diagnosis, studies have found. But clinical trials have also shown that when treatment is equal among study groups, racial differences in survival disappear, the report notes.
source: www.medscape.com
