Colorectal Cancer Screening: Guideline Recommends Starting at a Younger Age
Colorectal cancer (CRC) is the fourth most commonly diagnosed cancer in the United States and is one of the most common causes of cancer-related death.1 In 2019, around 146,000 adults were diagnosed with CRC, and an estimated 51,000 persons died from CRC.2
Despite the prevalence and severity of CRC, effective screening methods make it one of the most preventable cancers.1 Early detection of cancerous and precancerous lesions is key to survival, and in 2018 the American Cancer Society (ACS) lowered the recommended age to begin screening for individuals with average risk from 50 to 45 years old.1
This newsletter will review CRC and discuss the 2018 ACS screening recommendations and options for persons with an average risk of developing CRC.
How CRC Develops and Who Is at Risk
Most CRCs begin as adenomatous polyps that progressively enlarge, become dysplastic, and eventually become malignant.3 This process can take 10 or more years.3 The majority (70%) of colon cancers are sporadic and primarily linked to age and environmental factors.4 Approximately 10% are due to inherited (genetic) syndromes (eg, familial adenomatous polyposis [FAP] and Lynch syndrome), and 20% present as familial clustering without an identifiable genetic cause.4
The most important risk factor for CRC is age: approximately 80% of CRC occurs in persons 55 years of age or older.5 Another risk factor is family history; individuals with a first-degree relative with CRC have an approximately 2-fold greater risk than the average-risk population.6 Other risk factors for CRC, such as being overweight or obese, are modifiable (see Sidebar).1
Why Screen for CRC?
Screening programs help reduce the incidence of CRC by allowing identification and removal of adenomatous polyps. They also reduce death from the disease because most early-stage cancers are curable (the 5-year relative survival for CRC confined to the primary site is approximately 90% vs 14% for individuals with distant metastasis5). Compared with no endoscopic screening, a colonoscopy is associated with a 67% reduction in the risk of death from CRC.7 The effectiveness of screening is in large part due to the slow progression from formation of a polyp to malignant transformation.6
Despite the effectiveness of screening for CRC, only around 70% of adults in the United States 50 to 75 years old are up-to-date with CRC screening; about 1 in 3 adults are not getting screened as recommended.2 Screening rates are lower in racial and ethnic minorities and in those without insurance.8 Other barriers to CRC screening include not having a primary care provider, and providers not recommending screening to eligible patients.8.9 In addition, logistic factors such as difficulty scheduling, lack of transportation, lack of follow-up, forgetfulness, and lack of motivation contribute to suboptimal screening rates.8.9 One solution is providing reminders to patients and clinicians. Studies have shown that reminders increase CRC screening rates.10
ACS CRC Screening Guidelines for Average-Risk Individuals
The ACS 2018 guidelines for CRC screening recommend that average-risk adults aged 45 years and older undergo regular screening with either a high-sensitivity stool-based test or a structural (visual) exam.1 All positive results from non-colonoscopy screening tests should be followed up with a colonoscopy.1 The ACS decision to lower the age to begin screening took into account a 51% increase in the incidence of CRC in adults younger than 55 years from 1994 to 2014, and an 11% increase in mortality from 2005 to 2015.1
The ACS recommends that1
- Average-risk adults with a life expectancy of more than 10 years continue CRC screening through the age of 75 years.
- Screening decisions for individuals 76 through 85 years old should be based on patient preference, life expectancy, health status, and screening history.
- Screening for individuals older than 85 years should be discouraged.
Currently, other organizations have not lowered the recommended age to begin screening for average-risk individuals, but may do so. For example, the United States Preventive Services Task Force recently finalized and published its research plan for study of the effectiveness of CRC screening in average risk individuals ≥40 years of age.11
Importantly, the new ACS guidelines apply to individuals with an average risk of developing CRC. Persons at increased risk for CRC, such as those with a family history of CRC, polyps, and certain hereditary syndromes (eg, Lynch syndrome, FAP, see Sidebar), should begin screening earlier.5
Screening Options for CRC
CRC screening options include direct visualization methods, such as colonoscopy, and stool-based tests. Colonoscopy allows direct visualization and subsequent removal of lesions in the colon. Stool-based testing detects occult blood related to polyp growth, as well as other conditions (eg, diverticulitis). For persons with average risk of CRC, the ACS recommends screening with 1 of the following options1:
- Fecal immunochemical test (FIT) every year
- High-sensitivity, guaiac-based fecal occult blood test (gFOBT) every year
- Multitarget stool DNA test every 3 years
- Colonoscopy every 10 years
- Computed tomography colonography every 5 years
- Flexible sigmoidoscopy every 5 years
Any positive stool-based or imaging test should be followed up with colonoscopy.1
How Healthcare Providers Can Help
Healthcare providers can educate patients on the importance of screening for CRC, allay fears patients may have about undergoing a colonoscopy, and explain the alternatives to a colonoscopy, such as the gFOBT and FIT methods. They can also discuss modifiable risk factors for CRC (see Sidebar).