The American Cancer Society recommends all U.S. adults at average risk of colorectal cancer (CRC) undergo screening starting at age 45 years.

That update to ACS recommendations is based on an increasing burden of CRC in younger individuals, microsimulation modeling results, and a “reasonable expectation” that screening tests will perform as well in adults aged 45-49 years as they do in older adults, members of the ACS Guideline Development Group said in the guideline, which was published in CA: A Cancer Journal for Clinicians.

Starting screening at age 45 contrasts with recommendations from the U.S. Preventive Services Task Force (USPSTF), which in 2016 gave an “A” recommendation for CRC screening from 50 to 75 years of age. At the time, the USPSTF noted a modest increase in life-years gained by starting earlier, based on microsimulation modeling. But it concluded that available evidence best supported starting at age 50.

The updated ACS guidelines are based in part on a modeling study that the authors say extends the previous analysis conducted for the USPSTF.

“The recommendation places a high value on the potential years of life saved, addresses anticipated rising incidence going forward, and is expected to contribute to the reduction in disparities in incidence before age 50 years in some racial groups,” the ACS guideline authors added.

The recommendation to start screening at age 45 is a “qualified” recommendation, the authors said, given the limitations of the current evidence base. Most studies to date have been focused on older individuals, in keeping with long-standing recommendations to start screening at age 50.

The move downward in screening age recommendation acknowledges one of the most “significant and disturbing” developments in CRC, the guideline’s authors said: the marked increase in incidence among younger individuals.

While CRC incidence and mortality have been declining in adults aged 55 years and older, recent studies cited in the ACS guideline document show a 51% increase in incidence from 1994 to 2014 – and an 11% increase in mortality from 2005 to 2015 – for adults younger than 55 years.

The current age-specific incidence rate for adults 45-49 years is 31.4 per 100,000, compared with 58.4 per 100,000 in adults 50-54 years. However, the ACS guideline authors said the higher rate in the older cohort is partly influenced by more frequent screening. “The true underlying risk in adults aged 45-49 years is likely closer to the risk in adults aged 50-54 years than the most recent age-specific rates would suggest,” they wrote.

Since patients in this age range have not been routinely screened before, the ACS recommendation is based on modeling. Now we need to analyze the outcomes of early screening to identify which patients will benefit most. Choices for screening include either a structural examination or a high-sensitivity stool-based test, according to the guideline, which doesn’t state a preference for any particular test.

The AGA, in their statement in response, noted that with CRC rates rising in people younger than age 50, it is appropriate to consider beginning routine screening at age 45. The statement continues “Since patients in this age range have not been previously routinely screened, the ACS recommendation is based on modeling. Now we need to analyze the outcomes of early screening to identify which patients will benefit most.”

In addition to Dr. Wolf, members of the ACS Guideline Development Group received no compensation.

SOURCE: Wolf AMD et al. CA Cancer J Clin. 2018 May 30. doi: 10.3322/caac.21457.

ACS: Start colorectal cancer screening at age 45