Colorectal cancer (CRC)—cancer of the colon or rectum—is the third most commonly diagnosed cancer in the United States among both men and women and the third leading cause death in both men and women.  When men and women are combined in a single group, colorectal cancer is the second leading cause of death. 
The American Cancer Society estimates that in 2016 there will be: 
- 95,270 new cases of colon cancer
- 39,220 new cases of rectal cancer
- 49,190 deaths
The lifetime risk of developing colorectal cancer is 4.5% based on 2010-2012 data.  The median age for a diagnosis for colon cancer is 69 years in men and 73 years in women, while the median age for rectal cancer is 63 years for men and 65 years for women. 
In addition to age, the risk factors for developing CRC include family or personal history of CRC or colorectal polyps, hereditary syndromes such as familial adenomatous polyposis (FAP) or hereditary non-polyposis colorectal cancer (HNPCC), and personal history of chronic inflammatory bowel disease.  In addition to these risk factors, race also plays a role. African Americans have the highest incidence of colorectal cancer and the highest mortality rate of all racial groups.  Jews of Eastern European descent (Ashkenazi Jews) have the highest risk for developing colorectal cancer than any other ethnic group.  Lifestyle factors, such as obesity, physical inactivity, smoking, heavy alcohol consumption, a diet high in red or processed meat, and inadequate fruit and vegetable in take are also associated with an increased risk of developing colorectal cancer. 
In recent years, both the incidence and mortality of CRC have decreased in the United States. While all the reasons for this phenomenon are not known, factors that have been identified for improved mortality include risk-factor modifications, improvements in diagnostic techniques, more effective treatment, and increased screening resulting in early detection and prevention by polypectomy [7, 8]. Colonoscopy screening increased from 19.1% in 2000 to 54.5% in 2013 among adults aged 50 to 75 years.  While the mortality rate among blacks continues to be higher than the mortality rates among whites, the gap is shrinking. Annual declines in mortality rates from 2006 to 2010 were similar among black and white men (2.6% vs. 2.5%).  The difference in rates were slightly larger between black women and white women (3.3% versus 3.0%). 
The importance of early detection of CRC is evidenced by the observed differences in survival depending on the stage of disease at the time of diagnosis. The 5-year survival for patients with localized (penetration of the colon wall) disease is approximately 90.1%.  Unfortunately, only 40% of CRCs are identified at this stage.  The 5-year survival decreases to 70.4% when the disease reaches the regional stage and 12.5% once the cancer has reached the distant stage. 
Slow growing adenomatous polyps have been perceived as the precursor to colorectal cancer.  However, recent studies have found that certain types of serrated polyps pose a risk of malignant transformation through a serrated neoplasia pathway. [11, 12] Serrated polyps are more likely to be missed on colonoscopy and their progression to cancer may be more rapid.  Researchers encourage physicians to recognize the importance of serrated polyps and their role in colorectal cancer and to be aware of the latest guidelines. 
The American Cancer Society recommends screening for colorectal cancers as the most powerful means of preventing the colorectal cancer.  The overall screening rates for CRC in the United States have been rising over the last several years, increasing from 54% in 2002 to 65 percent in 2010.  Among blacks and whites the percentage who reported being up-to-date with CRC screening were nearly equivalent and higher than those for other races in 2012.  However, screening rates remain lower among persons with lower income, no health insurance, or less than a college education. 
Although CRC screening rates are improving overall, a significant proportion of the population are not receiving appropriate screening.  CRC screening rates are lower than other cancer screenings, such as breast cancer and cervical cancer, and despite the lack of evidence regarding PSA testing, more men in the United States undergo prostate cancer screening than CRC screening. [16, 17] Increasing the proportion of adults receiving regular screening is thought to have the greatest potential and most immediate impact for reducing the incidence and mortality of CRC.  One projection estimates that CRC mortality could decrease by 50% by the year 2020 if screening use increased to 70% annually and other interventions such as decreasing lifestyle risk factors (e.g. smoking, obesity, red meat consumption) were employed. 
Several studies have presented evidence showing a physician recommendation is one of the most influential factors and predictors of whether a patient undergoes screening for CRC. [8, 19, 20] A physician recommendation is essential to increasing colorectal cancer screening rates and the magnitude of the effect of a recommendation is considerable.  Patients who report receiving a recommendation are much more likely to undergo screening than patients who have not received a recommendation. [18-22] The most common reason for not undergoing screening was the lack of a physician recommendation.  There are multiple barriers to screening, including, but not limited to, the lack of awareness of the importance of CRC screening, lack of knowledge or uncertainty of screening guidelines, and lack of patient insurance coverage. 
In 2008, the American Cancer Society, the US Multi-Society Task Force on Colorectal Cancer, and the American College of Radiology released jointly developed guidelines updating the organizations' prior independently produced guidelines on the screening recommendations for CRC in average risk adults. The new recommendations include two new screening tests: computed tomographic (or virtual) colonography (CTC) and the stool DNA (sDNA) test. The revised guideline differs from the previous guidelines in that the screening tests are grouped into those that primarily detect cancer and those that can detect cancer, as well as adenomatous polyps. This distinction was made in order to help primary care physicians engage in shared-decision making with their patients and increase understanding of the advantages and disadvantages between the tests.  The organizations strongly support prevention as the main goal of screening and preference is given for tests that can detect both polyps and cancer. 
The 2008 updated screening recommendations from both the USPSTF and the ACS/Multi-Society Task Force consensus guidelines panel state that CRC screening by fecal occult blood testing should be performed with high-sensitivity FOBT - defined as either a fecal immunochemical test or a highly sensitive guiaic-based fecal test (such as Hemoccult SENSA).  Hemoccult II and other older versions of guiaic-based tests have been found to have lower sensitivity for cancer detection than FIT or SENSA and should no longer be used for CRC screening.  The guidelines recommend that CRC screening for persons of average risk and no symptoms of colon cancer should begin at age 50 with one of the following tests: 
- Structural tests that examine the colon itself can detect adenomatous polyps and cancer:
- Flexible sigmoidoscopy every 5 years or
- Colonoscopy every 10 years or
- Double contrast barium enema (DCBE) every 5 years or
- Computed tomographic (or virtual) colonography (CTC) every 5 years
- Stool tests that mainly detect cancer:
- Annual high sensitivity guaiac-based fecal occult blood test (gFOBT) or
- Annual fecal immunochemical test (FIT) with high test sensitivity for cancer or
- Stool DNA test with high sensitivity for cancer (interval unknown)
Clinical Note: Annual screening with high-sensitivity gFOBT (such as Hemoccult SENSA) that have been shown in the published, peer-reviewed literature to detect a majority of prevalent CRC in an asymptomatic population is an acceptable option for colorectal screening in average-risk adults aged 50 years and older. Any positive test should be followed up with colonoscopy.
Commonly used guaiac tests, with or without rehydration, that have not been shown in the literature to detect a majority of prevalent CRC at the time of testing are no longer recommended (such as Hemoccult II).
Any abnormal stool test should be followed up with a colonoscopy. A colonoscopy is also indicated if flexible sigmoidoscopy or DCBE tests are positive. Each screening test has advantages, disadvantages, and associated risks and limitations, which will be reviewed later in the module. The jointly developed guidelines did not include an update of the recommendations for individuals at increased and high risk for CRC. In general, recommendations for individuals at increased risk are for earlier and more frequent screening/surveillance with a structural test to allow a direct examination of the rectum and colon. 
CRC screening is one of the clinical performance measures for preventive care and screening. The Centers for Medicare & Medicaid Services (CMS) 2016 Physician Quality Reporting Initiative (PQRI) includes a measure on CRC screening: 2016 PQRS Measure #113: Colorectal Cancer Screening. The measure is defined as the percentage of patients aged 50 through 75 years who received the appropriate colorectal cancer screening during the one-year measurement period. This measure excludes patients at increased or high risk who require more intensive screening and surveillance.
This module will focus on CRC screening for the average risk patient. Patients at increased risk or high risk for CRC will be excluded for the purposes of this module. In general, recommendations for individuals at increased risk or high risk are more intensive. The frequency of screening/surveillance for increased risk or high risk will vary depending on the specific risk factor(s) for each patient.
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- Boursi B, Sella T, Liberman E, et al. The APC p.I1307K polymorphism is a significant risk factor for CRC in average risk Ashkenazi Jews. European Journal of Cancer. 2013;49(17):3680–3685.
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