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Colorectal cancer screening: Choosing the right test

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ABSTRACT

Colorectal cancer, the second most common type of cancer and cause of cancer-related deaths in the United States, can largely be prevented by screening. The 2 most used methods in the United States are colonoscopy and fecal immunochemical testing (FIT). FIT is noninvasive but must be done yearly for optimal performance and, if positive, must be followed by colonoscopy. Colonoscopy is invasive, operator-dependent, and more expensive, but it can detect and remove polyps during the same procedure. The choice of test depends on patient preference, family history, and the likelihood of compliance.

KEY POINTS

  • Colorectal cancer rates are increasing in young individuals, with 10,000 new cases reported in 2017 in people ages 20 to 49. The evidence to support screening at ages 45 to 50 is not well established.
  • FIT is noninvasive but requires high patient adherence and the ability to follow a multistep process. Preliminary results from one trial showed it inferior to colonoscopy for detecting colorectal cancer precursors.
  • Colonoscopy allows visualization and removal of precursor lesions. A positive FIT result requires follow-up colonoscopy within 10 months.


 

References

Screening can help prevent colorectal cancer. The United States has seen a steady decline in colorectal cancer incidence and mortality, thanks in large part to screening. Screening rates can be increased with good patient-physician dialogue and by choosing a method the patient prefers and is most likely to complete.

In this article, we review a general approach to screening, focusing on the most commonly used methods in the United States, ie, the guaiac-based fecal occult blood test (FOBT), the fecal immunochemical test (FIT), and colonoscopy. We discuss current colorectal cancer incidence rates, screening recommendations, and how to choose the appropriate screening test.

This article does not discuss patients at high risk of polyps or cancer due to hereditary colon cancer syndromes, a personal history of colorectal neoplasia, inflammatory bowel disease, or primary sclerosing cholangitis.

TRENDS IN INCIDENCE

Colorectal cancer is the second most common type of cancer and cause of cancer-related deaths in the United States, responsible for an estimated 50,000 deaths in 2017. The lifetime risk of its occurrence is estimated to be 1 in 21 men and 1 in 23 women.1 Encouragingly, the incidence has declined by 24% over the last 30 years,2 and by 3% per year from 2004 to 2013.1 Also, as a result of screening and advances in treatment, 5-year survival rates for patients with colorectal cancer have increased, from 48.6% in 1975 to 66.4% in 2009.2

When detected at a localized stage, the 5-year survival rate in colorectal cancer is greater than 90%. Unfortunately, it is diagnosed early in only 39% of patients. And despite advances in treatment and a doubling of the 5-year survival rate in patients with advanced cancers since 1990,3 the latter is only 14%. In most patients, cancer is diagnosed when it has spread to the lymph nodes (36%) or to distant organs (22%), and the survival rate declines to 71% after lymph-node spread, and 14% after metastasis to distant organs.

It is essential to screen people who have no symptoms, as symptoms such as gastrointestinal bleeding, unexplained abdominal pain or weight loss, a persistent change in bowel movements, and bowel obstruction typically do not arise until the disease is advanced and less amenable to cure.

Increasing prevalence in younger adults

Curiously, the incidence of colorectal cancer is increasing in white US adults under age 50. Over the last 30 years, incidence rates have increased from 1.0% to 2.4% annually in adults ages 20 to 39.4 Based on current trends, colon cancer rates are expected to increase by 90% for patients ages 20 to 34 and by 28% for patients 35 to 49 by 2030.5

Although recommendations vary for colorectal cancer screening in patients under age 50, clinicians should investigate symptoms such as rectal bleeding, unexplained iron deficiency anemia, progressive abdominal pain, and persistent changes in bowel movements.

Other challenges

Despite the benefits of screening, it is underutilized. Although rates of compliance with screening recommendations have increased 10% over the last 10 years, only 65% of eligible adults currently comply.1,6

Additionally, certain areas of the country such as Appalachia and the Mississippi Delta have not benefited from the decline in the national rate of colorectal cancer.7

SCREENING GUIDELINES

Most guidelines say that colorectal cancer screening should begin at age 50 in people at average risk with no symptoms. However, the American College of Gastroenterology (ACG) recommends beginning screening at age 45 in African Americans, as this group has higher incidence and mortality rates of colorectal cancer.8 Also, the American Cancer Society recently recommended beginning screening at age 45 for all individuals.9

Screening can stop at age 75 for most patients, according to the ACG,8 the US Multi-Society Task Force on Colorectal Cancer,10 and the US Preventive Services Task Force (USPSTF).11 However, the decision should be individualized for patients ages 76 to 85. Patients within that age group who are in good health and have not previously been screened are more likely to benefit than those who have previously been screened and had a negative screening test. Patients over age 85 should not begin or continue screening, because of diminished benefit of screening in this age group, shorter life expectancy, advanced comorbid conditions, and the risks of colonoscopy and cancer treatment.

Patients and clinicians are encouraged to collaborate in deciding which screening method is appropriate. Patients adhere better when they are given a choice in the matter.12–14 And adherence is the key to effective colorectal cancer screening.

Familiarity with the key characteristics of currently available colorectal cancer screening tests will facilitate discussion with patients.

Opportunistic vs programmatic screening

Screening can be classified according to the approach to the patient or population and the intent of the test. Most screening in the United States is opportunistic rather than programmatic—that is, the physician offers the patient screening at the point of service without systematic follow-up or patient re-engagement.

In a programmatic approach, the patient is offered screening through an organized program that streamlines services, reduces overscreening, and provides systematic follow-up of testing.

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