Start Screening for Colon Cancer at Age 45, Not 50, ACS Recommends

Rates of colon cancer are increasing in younger people, and as a result the American Cancer Society (ACS) is recommending that screening should start 5 years earlier, at 45 years of age rather than 50.

The new guidelines are based on incidence rates, the ACS said Wednesday.

"When we began this guideline update, we were initially focused on whether screening should begin earlier in racial subgroups with higher colorectal cancer incidence, which some organizations already recommend," Richard C. Wender, MD, the society’s chief cancer control officer, said in a statement. "But as we saw data pointing to a persistent trend of increasing colorectal cancer incidence in younger adults, including American Cancer Society research that indicated this effect would carry forward with increasing age, we decided to reevaluate the age to initiate screening in all US adults."

The updated recommendations were published Wednesday in CA: A Cancer Journal for Clinicians, an ACS journal. The guidelines were last updated 10 years ago, and the ACS said it does not know why the rates are increasing, although it noted that almost 40% of currently eligible adults (meaning those over 50) are not getting screened.

The recommendation does not mean that every adult over 45 is limited to a traditional colonoscopy, which involves fasting and preparation that many people find unpleasant. Instead, the ACS says there are a number of options, and the new guideline does not prioritize the screening test options, since adults have different preferences.

The options are:

• An annual fecal immunochemical test
• An annual high sensitivity guaiac-based fecal occult blood test
• A multi-target stool DNA test every 3 years
• A colonoscopy every 10 years
• A CT colonography every 5 years
• Flexible sigmoidoscopy every 5 years

All positive results on the non-colonoscopy screening tests should be followed up with a colonoscopy.

The ACS said average-risk adults in good health with a life expectancy of greater than 10 years should continue screening through age 75. Clinicians should individualize screening decisions for people ages 76 through 85, and should discourage patients over age 85 from continuing screening.

Colon cancer incidence has fallen steadily over the past 20 years in people 55 and over due to screening that results in removal of polyps that can turn cancerous, as well as changes in exposure to risk factors.

However, in people under 50, there has been a 51% increase in colon cancer since 1994. Death rates in this group have also begun to rise in recent years, indicating that increased incidence rates do not appear to come from increased use of colonoscopy alone.

Another analysis found that adults born around 1990 have 4 times the risk of rectal cancer compared with adults born around 1950, who have the lowest risk.

Risk factors for colon cancer include:

• Cigarette smoking
• Obesity, which is rising among Americans
• Poor diet, including high consumption of alcohol and red and processed meat and low consumption of fruits/vegetables, dietary fiber, and dietary calcium
• Low rates of physical inactivity

Other studies have pointed to the use of aspirin; presence of hereditary colon cancer conditions; a family history; and certain medical conditions, including chronic inflammatory bowel disease, type 2 diabetes, and a history of abdominal or pelvic radiation for a previous cancer.

In 2016, 2 of 3 microsimulation models conducted for the United States Preventive Services Task Force (USPSTF) screening recommendations suggested that starting screening with an interval of 15 years at age 45 versus age 50 provided a slightly more favorable balance between the benefits and burden of screening. But the USPSTF elected not to recommend the younger starting age in 2016.

ACS commissioned a new modeling study to incorporate more recent studies of the rising incidence trends in younger adults. The new models showed that multiple screening strategies beginning at age 45, including colonoscopy at the conventional 10-year interval, were beneficial.

Colon cancer is the fourth most commonly diagnosed cancer among US adults in the United States and is the second leading cause of cancer deaths.

Reference

Wolf AMD, Fontham ETH, Church TR, et al. Colorectal cancer screening for average‐risk adults: 2018 guideline update from the American Cancer Society [published online May 30, 2018]. CA Cancer J Clin. doi: 10.3322/caac.21457.