Why Screen for Colorectal Cancer?

Colorectal Cancer (CRC) is the third most common form of malignancy among both men and women and the second overall leading cause of cancer deaths in the United States.  American Cancer Society (ACS) projections for the year 2008 include 148,810 new cases of colorectal cancer, and 49,960 deaths from CRC. (1)  This accounts for about 10% of all cancer deaths

The encouraging news is that CRC is preventable through appropriate screening measures.  Morbidity and mortality from CRC can be reduced significantly through early detection and removal of adenomatous polyps or localized cancerous lesions. 

Natural History of CRC

Development of CRC is a slow, progressive process.  Over 95% of colorectal cancers arise from benign adenomas, a majority of which are polypoid. (6) Malignant transformation of adenomas depends largely on their tissue classification (tubular, villous, or tubulovillous) and their size.  Villous adenomas and those greater than or equal to 1cm carry a greater potential for transformation. (7)

The natural history of the sequence from the beginning of adenomatous polyp growth to the development of cancer is about 10-15 years. (8)  This unusually long pre-clinical phase means that there is a high potential for screening to reduce both morbidity and mortality.  The goal of CRC screening is to detect and remove lesions at the earliest, most benign stage possible. 

Screening and CRC Survival 

As with other malignancies, 5-year survival depends on stage at diagnosis.  Screening increases the chance of catching CRC at an early stage.

Ries L, Melbert D, Krapcho M, et al. SEER Cancer Statistics Review, 1975–2004. Bethesda, MD: National Cancer Institute; 2007.

• Localized disease is defined as an invasive malignancy confined to the organ of origin.


• Regional disease is defined as a cancer that has affected adjacent organs or lymph nodes or both.


• Distant disease is defined as a malignancy that has metastasized.

Incidence rates of CRC have declined over most of the last twenty years.  New cases have decreased from 66.3 per 100,000 people in 1985 to 48.2 cases per 100,000 in 2004.  Incidence rate decreased most quickly from 1998 to 2004, at 2.3% per year; this is thought to be due in part to an increase in screening. (13)

When to Screen

The lifetime risk for developing CRC for both men and women is approximately 1:19 or 5.4%. (21) However, risk changes dramatically with age.  In fact, 90% of people who are found to have CRC are 50 years or older.

The ACS, as well as many major authorities including the United States Preventive Services Task Force and the American College of Gastroenterology, advocatesregular CRC screening for average risk, asymptomatic patients beginning at age 50. (13,9)

Figure 1. Age-incidence curve for colorectal cancer for an average-risk population. For those without a significant family history or other predisposing factors, the risk begins to increase substantially after age 50. (American Gasteroenterological Association.)

Quality Measurements

In 2004, the National Committee for Quality Assurance (NCQA) announced a colorectal cancer screening measure to be included in the Health Plan Employer Data and Information Set (HEDIS).  HEDIS is a national system that monitors the quality of care and the performance of managed care plans.  The colorectal cancer screening measure is consistent with the screening recommendations supported by the CDC and the U.S. Preventive Services Task Force.  Recent updates to the American Cancer Society guidelines are not reflected, as of early 2008.

The measure assesses the proportion of eligible health plan members between the ages of 50 and 80 who have received either fecal occult blood testing within the past year, flexible sigmoidoscopy within the past 5 years, colonoscopy within the past 10 years, or double contrast barium enema within the past 5 years. (4)

Screening Options

The ACS, in a 2008 guideline issued in cooperation with the US Multi-Society Task Force on Colorectal Cancer and the American College of Radiology, recommends that both men and women follow one of the following screening regimens.  (The US Multi-Society Task Force comprises the American College of Gastroenterology, American Gastroenterological Association, and American Society for Gastrointestinal Endoscopy.)  There is insufficient data to determine which screening test is best in terms of balance of benefits and potential harms or cost-effectiveness.  Since each option has advantages and disadvantages, the choice of screening modality should be based on patient preference, medical contraindication, patient adherence, and available resources for testing and follow-up. (2)

In addition, the current ACS guideline emphasizes the fact that some tests are more likely than others to detect precancerous polyps.  Imaging tests and direct visualization will reveal both polyps and cancerous tumors, with the potential to prevent cancer via colonoscopic clearing of polyps.  Tests that reveal blood or tumor DNA in the stool primarily serve to detect cancer.  In either case, if cancer is detected, screening increases the chance that it will be found at an early, treatable stage. 

Adapted from: Levin B, et al.  Screening and surveillance for the early detection of colorectal cancer and adenomatous polyps, 2008: a joint guideline from the American Cancer Society, the US Multi-Society Task Force on Colorectal Cancer, and the American College of Radiology.  CA Cancer J Clin.  March 5, 2008; e-pub ahead of print.

As of early 2008, the CDC (incorporating the 2002 U.S. Preventive Services Task Force [USPSTF] recommendations) continued to support the following screening options:

Source:  http://www.cdc.gov/cancer/colorectal/basic_info/screening/guidelines.htm

Screening Utilization

Despite extensive literature on the burden of disease and the guidelines of national authorities, CRC screening is still underutilized.  In the 2003 National Health Interview Survey (NHIS), screening rates varied by gender, race, education, health insurance coverage, and immigration status, but were lowest for those without insurance. (19)  Poor and uninsured people are more likely to be treated for cancer at later stages and therefore more likely to die from cancer than people of higher socioeconomic status.

The NHIS revealed that only 16.3% of non-Hispanic white adults had a fecal occult blood test (FOBT) within the last year and only 37.5% had some form of endoscopy within the past five years.  African American adults had similar rates of FOBT screening; the endoscopy rate was lower at 32.6%.  Hispanic men and women were even less likely to be screened for CRC, with rates of 11.9% for FOBT within the last year and 25.1% for endoscopy. (19)  All of these screening rates fell far short of the ACS 2015 objectives of 75% for people over the age of 50.

Racial Disparities in Colorectal Cancer

Overall, African Americans are more likely to develop and die from cancer than any other ethnic or racial group. (13)  Both incidence rates and mortality for CRC are higher than in whites.  Among African American adults, CRC is the third leading cause of cancer mortality. The five-year survival rate for CRC in African Americans during the period from 1996-2002 was 57%.  This is an improvement over the 1975-77 rate of 46%.  However, the improvement was smaller than that for whites, for whom five-year survival increased during the same time period from 51% to 66%.  This disparity is at least partly attributable to the later stage at diagnosis for African Americans (18)

CRC incidence and mortality rates for Hispanic men and women are lower than those for African Americans and non-Hispanic whites.  But, CRC remains the third most commonly diagnosed cancer among Hispanic adults.  In addition, it is the third leading cause of cancer death in Hispanic women and matches prostate cancer as the second leading cause of cancer death in Hispanic men.  As with African Americans, the annual reduction in CRC mortality in Hispanics in the 1990s was smaller than that for non-Hispanic whites. (20)