Running head: COLORECTAL SCREENING: RECOMMENDATION FOR
COLONOSCOPY
Katelyn Strasser
Colorectal screening: Recommendation for colonoscopy
October 22, 2013
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Background
Screening for colorectal cancer is paramount in reducing the number of deaths
from this disease. Colorectal cancer is the second leading cause of cancer-related death
in America (CDC, 2013). It is also a worldwide problem, with an incident rate of 1
million new cases each year and more than 500,000 deaths from the cancer each year.
The aging population in the world is a factor that will only increase the occurrence of this
disease in the future (World Gastroenterology Organisation, 2007). Colorectal cancer
affects both men and women. In 2009, 26,806 men and 25,042 women died of this
cancer. The areas most affected by this cancer are North America, Australia, New
Zealand, and parts of Europe. For this reason, it is often called a disease of Western
lifestyle. (WGO, 2007)
Colorectal cancer is cancer of the colon or rectum, and is often referred to as
colon cancer. Age and family history play major roles in the risk of colon cancer (WGO,
2007). Over 90% of cases of the cancer happen in people who are 50 or older (CDC,
2013). Colorectal cancer may have the greatest familial link of any type of cancer. Ten
to thirty percent of people diagnosed with colorectal cancer have a family history of the
disease. Having had a relative with the cancer increases relative risk significantly. For
example, a person with a first-degree relative who had colorectal cancer between the ages
of 45 and 59 has a relative risk of 2.25 of developing the cancer. If a first-degree relative
had colorectal cancer below the age of 45, that family member would have a relative risk
of 3.87 for developing the cancer (WGO, 2007).
Although colorectal cancer causes many deaths, about 60% of these deaths could
be prevented if everyone over the age of 50 had regular screening tests (CDC, 2013).
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Colon screening tests allow doctors to remove polyps, which are precancerous masses
found in the intestinal lumen. These polyps can turn into cancerous adenomas, so it is
important to have them removed before they reach that point in their growth. Screening
tests for this type of cancer include an occult blood test, flexible sigmoidoscopy,
colonoscopy, double-contrast barium enema, and computed-tomographic colonography
(WGO, 2007).
The fecal occult blood test (FOBT) is the most inexpensive and least invasive way
to screen for colorectal cancer. In this test, a stool sample is collected and analyzed for
small amounts of blood (National Cancer Institute, 2013). The basis for this test is that it
identifies the blood and tissue shed by cancerous tumors before clinical symptoms are
present. FOBT has been shown to decrease colorectal cancer mortality by sixteen percent
(Wilkins & Reynolds, 2008). Although this test is proficient at detecting blood from
cancerous polyps, it also reacts to certain foods such as fruits, vegetables, and red meat
that lead to false-positive results (WGO, 2007). For a one-time FOBT, the sensitivity is
only about 50-60%, although when done every year or two over an extended period of
time, sensitivity increases to 90%. Low sensitivity has negative consequences such as a
large amount of false-negative results and a false reassurance to patients that they do not
have cancer. Positive predictive values range from 5% to 18.7% (NCI, 2013). The
specificity for this test is about 95.2% (WGO, 2007). One type of fecal occult blood test
that is gaining popularity is the fecal immunochemical test. Sensitivity is higher than the
guaiac-based testing, but with a slightly higher rate of false-positives (Wilkins &
Reynolds, 2008).
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The flexible sigmoidoscopy is the next screening test used for colorectal cancer.
This test uses a flexible endoscope to let the physician examine the inner surface of the
large intestine up to about 60cm from the anal opening. With this test, the physician can
see polpys and remove or take tissue samples of them. Studies following this screening
have reported a 28% relative reduction in colorectal cancer mortality. The specificity of
this procedure is 98-100 percent. Sensitivity for cancer is lower at 35% to 70% because
the adenomas on the right side of the colon are missed with this procedure. Taking into
account just the left side of the colon, the sensitivity for cancer is about 95% (WGO,
2007). This test may be most beneficial for white males. Women as twice as likely to
have an adenoma in an area that cannot be reached by a flexible sigmoidoscopy. African
Americans are also more likely to have a large polyp beyond 60cm in the colon (Wilkins
& Reynolds, 2008).
A colonoscopy is similar to a flexible sigmoidoscopy, but it screens the entire
length of the colon for polyps and other masses. This procedure is often considered the
“gold standard” for colorectal screening because both the specificity and sensitivity for
detecting colon cancer and polyps are around 95% (USPSTF, 2013). A 90% reduction in
the incidence and mortality with the use of colorectal cancer has been predicted (WGO,
2007).
Two lesser-used screening tests are the double-contrast barium enema and
computed tomographic colonoscopy. The double-contrast barium enema was used to
detect polyps before the colonoscopy appeared in the 1970s. It is sometimes still used
when a physician cannot for one reason or another reach the scope all the way through
the right side of the colon. Both specificity and sensitivity for colon cancer are lower for
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this test than a colonoscopy (Wilkins & Reynolds, 2008). Sensitivity is around
48%.(WGO, 2007) Computed tomographic colonography uses CT scan images to find
polyps. Sensitivities of this test range from 55 to 100 percent and specificities are from
86 to 98 percent for finding polyps that are greater than 10mm in size (Wilkins &
Reynolds, 2008). Specificity and sensitivity vary so much because this test has
specificity and sensitivity for very large polyps, but low numbers for medium and small
polyps. (WGO, 2007).
Benefits and drawbacks exist for each type of screening test. Although the fecal
occult blood test is the simplest test, sensitivity for one-time use is low, and many falsepositives occur (WGO, 2007). Flexible sigmoidoscopy is safer and costs less than a
colonoscopy. Also, patients are often not sedated during the procedure. This improves
safety during the procedure as patients can give feedback, limiting barotrauma or
abrasions to the colon. However, flexible sigmoidoscopies do not cover the entire colon
and can miss cancerous lesions. Colonoscopies have both high sensitivity and specificity
for detecting colorectal cancer, but they also carry a greater risk of perforation and
adverse effects. Patients are sedated during this procedure, causing them to miss a day
from work. The patient also has to complete an unpleasant bowl preparation the day
before, and the test itself can be expensive without insurance. One study indicated that
the median cost of this procedure in the United States was $1,736. Double contrast
barium enemas are very safe, but do not have a high detection rate of small polyps.
Computed tomographic colonography again requires a bowel preparation and has varying
sensitivities, but carriers less chance of perforation than a colonscopy (Wilkins &
Reynolds, 2008).
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Rates of colorectal screening in the United States vary by race, socioeconomic
status, and demographic area of populations. The Behavioral Risk Factor Surveillance
System identified the percentage of adults by state in America ages 50-75 who were upto-date with colorectal test screening. Many of the Northeastern states had the highest
rates, with 69.0 to 75.2 percent of the population being up-to-date with screening. Some
of the states with the lowest percentage of screening (54.1 to 59.2 percent) include
southern states like Texas, Mississippi, and Arkansas, and Northwestern states like
Montana, Idaho, and Wyoming (CDC, 2013).
Colorectal cancer disproportionately affects people of different races and
ethnicities. In the United States, black Americans have the highest incident rate of
colorectal cancer, followed by white, Hispanic, Asian/Pacific Islander, and American
Indian/Alaska Native people. The incidence rate in black males is 72 per 1000,000 and
in black females it is 55 per 100,000. White males have an incidence rate of 68 per
100,000 and 48 out of 100,000 females each year will be diagnosed with colorectal
cancer. Mortality rates are even more disproportionate, with 35 per 100,000 black male
deaths and 25 per 100,000 black female deaths due to colorectal cancer. This is in
comparison with just 25 per 100,000 white males deaths and 17 per 100,000 white female
deaths (CDC, 2013). Higher numbers of advanced stage disease and lower 5-year
survival rates in African Americans play a role in higher mortality rates. Studies have
found that only 38.9% of African Americans older than 50 have had some type of
colorectal screening while 44.2% of whites have had a screening test (Purnell et al.,
2010).
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Factors such as traditional cultural orientation, group susceptibility of colorectal
cancer, physician ethnicity, and medical mistrust have contributed to lower screening
rates in African Americans. Members of this group that have a more traditional cultural
orientation are less likely to be screened, but more can be persuaded to have a test if they
believe that they are more at risk for the disease. African Americans also prefer to have
physicians of their same ethnicity, and their general mistrust of medical professionals can
also negatively affect their desire to be screened (Purnell et al., 2010). African
Americans may also have more limited access to medical care and lower rates of medical
insurance, restricting their abilities to pay for the screening tests (Patel et al., 2012).
Public health screening tests for colorectal cancer bring about many ethical
considerations. It is the role of a public health professional, specifically an
epidemiologist, to evaluate the characteristics of a screening test. A good screening test
will be simple, rapid, inexpensive, safe, and acceptable. Part of the reason to have a good
screening test is that offering a test with these characteristics will maintain public trust.
Respecting cultural diversity is part of gaining public trust, and is key in implementing
public health programs and improving the health of a population. In researching types of
screening tests, epidemiologists should weigh the risks and benefits, protect
confidentiality and privacy, and obtain informed consent from participants. In promoting
screening for colorectal cancer, public health professionals should be advocates for those
affected by this disease, especially the more vulnerable populations. Epidemiologists are
able to share data that reflects the need for colorectal screening and use this information
to let the public know where the greatest need is (Friis & Sellers, 2014).
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Recommendation
Recommending a screening test for colorectal cancer is complicated because of
the various types of tests, and the risks and benefits associated with each. In my home
state of South Dakota, it is predicted that 430 new cases of colorectal cancer will be
diagnosed in 2013. In the same year, 150 deaths will be attributed to this cancer
(SDDOH, 2013). Early detection can reduce the rates of cancer and mortality in this
state. Even between different public health services, debate exists as to which screening
test is best to use. The U.S. Preventive Services Task Force (2008) recommends using
the fecal occult blood testing, sigmoidoscopy, or colonoscopy in adults between the ages
of 50 and 75. The American Cancer Society (2013) supports every test listed in the
background section of this paper, with certain stipulations based on the risk factors of the
person being tested.
My recommendation to the people of South Dakota would be that people over 50
years of age with average risk for colon cancer receive a colonoscopy every 10 years.
Average risk means that a person does not have inflammatory bowel disease, a personal
or family history of colorectal cancer, or a genetic syndrome like adenomatous polyposis
or hereditary nonpolyposis colorectal cancer (CDC, 2013). My recommendation is based
on the evidence that the colonoscopy has the highest sensitivity and specificity of all
screening tests. This test is able to not only detect polyps and cancer, but also remove the
polyps at the same time. Although the test is the most expensive option, it is cost saving
when compared to chemotherapy and other treatments for colorectal cancer.
Additionally, many health insurance plans cover the cost of preventative screening tests
such as this one. Some states have passed laws requiring insurance companies pay for
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colorectal cancer screening tests, and the Affordable Care Act mandates coverage of
these tests (American Cancer Society, 2013). I recommend that a board certified
gastrointestinal physician or general surgeon who is trained in colonoscopies perform this
procedure.
Public health will play a vital role in increasing participation levels in colorectal
screening. This first step in increasing participation is making people recognize the need
for screening. Public health professionals should inform the public that it is the second
leading cause of cancer related deaths, but that 6 out of every 10 deaths could be
prevented if routine screening occurred. A major part of public health’s duty is to
educate the public. People should be given information about both genetic and lifestyle
risk factors for the disease. Lifestyle factors that can contribute to colorectal cancer
include a diet low in fruits, vegetables, and fiber, or a high fat diet; lack of regular
physical activity; overweight and obesity; and alcohol or tobacco use. Most people will
recognize that they have at least one of those factors (CDC, 2013). Another beneficial
component to education would be information on the colonoscopy procedure. Because of
the bowel preparation, the screening test tends to have a negative connotation. Education
in the form of fliers, ads, or commercials sponsored by public health programs could
focus on the basic steps of a colonoscopy.
Other barriers to people having colorectal cancer screenings are access and
money. State and local health departments have the opportunity to share resources with
their communities about colorectal screening. For example, South Dakota Department of
Health (2013) promotes programs that offer assistance for colonoscopies to low-income
individuals. Increasing screening participation may, in some cases, be as simple as
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informing people how affordable a colonoscopy would be. Some people with health
insurance may not realize that part of or all of the fee for a colonoscopy may be covered
by their insurance. Public health professionals should also advocate for new programs
that offer monetary assistance for screenings, and encourage primary physicians and
other health professionals working in community clinic setting to educate their patients
on screenings.
Increased rates of screening for colorectal cancer can significantly decrease the
rates of cancer and mortality. I recommend a colonoscopy every ten years for those at
average risk over the age of 50. The colonoscopy has the highest specificity and
sensitivity of all tests, and can remove precancerous polyps and biopsy other masses.
Public health professionals should promote colonoscopies and support programs that
provide monetary assistance to those whose insurance does not cover or help to cover the
cost of this screening.
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References
American Cancer Society. (2013). Colon and rectum cancer. Retrieved from
http://www.cancer.org
Centers for Disease Control and Prevention. (2013). Colorectal (colon) cancer.
Retrieved from http://www.cdc.gov/cancer/colorectal
Friis, R. H., & Sellers, T. A. (2014). Epidemiology for public health practice.
Burlington, MA: Jones & Bartlett Learning.
National Cancer Institute. (2013). Colorectal cancer screening (PDQ). National
Institutes of Health. Retrieved from
http://www.cancer.gov/cancertopics/pdq/screening/colorectal/HealthProfessional/
page3
Patel, K., Hargreaves, M., Liu, J., Kenerson, D., Neal, R., Takizala, Z., & ... Blot, B.
(2012). Factors Influencing Colorectal Cancer Screening in Low-Income African
Americans in Tennessee. Journal Of Community Health, 37(3), 673-679.
doi:10.1007/s10900-011-9498-8
Purnell, J., Katz, M., Andersen, B., Palesh, O., Figueroa-Moseley, C., Jean-Pierre, P., &
Bennett, N. (2010). Social and cultural factors are related to perceived colorectal
cancer screening benefits and intentions in African Americans. Journal Of
Behavioral Medicine, 33(1), 24-34. doi:10.1007/s10865-009-9231-6
South Dakota Department of Health. (2013). Cancer control SD. Retrieved from
http://getscreened.sd.gov
U.S. Preventive Services Task Force. (2008). Screening for colorectal cancer. Retrieved
from http://www.uspreventiveservicestaskforce.org/uspstf/uspscolo.htm
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Wilkins, T., & Reynolds, P. L. (2008). Colorectal cancer: A summary of the evidence for
screening and prevention. American Family Physician. 15; 78(12).
Retrieved from http://www.aafp.org/afp/2008/1215/p1385.html
World Gastroenterology Organisation. (2007). World gastroenterology
organisation/international digestive cancer alliance practice guidelines: Colorectal
cancer screening. Retrieved from http://www.worldgastroenterology.org/assets/
downloads/en/pdf/guidelines/06_colorectal_cancer_screening.pdf