Roxanne Nelson, BSN, RN
May 30, 2018
For persons at average risk, screening should begin at age 45 rather than 50. The change in age is based in part on recent data demonstrating a rise in colorectal cancer among younger populations.
"This new recommendation is based on new evidence of rising incidence, and modeling studies that showed an improvement in life years gained, and a favorable balance of benefits and harms after incorporating the new incidence data into models," said Robert Smith, PhD, vice president of cancer screening at the ACS.
These are the models used by the US Preventive Services Task Force (USPSTF), Smith told Medscape Medical News. "So, while this guideline differs from the USPSTF recommendation by recommending screening should begin at age 45, we feel it is a credible recommendation, based on the new data," he said.
The recommendation to begin screening at age 45 years is a qualified recommendation. It was the only change made to the current ACS guidelines. The new guideline maintains the status quo in that it does not prioritize among the various screening test options that are available but recommends regular screening with either a high-sensitivity stool-based test or a structural (visual) exam, depending on patient preference and test availability.
The updated recommendations were published online May 30 in CA: A Cancer Journal for Clinicians.
Guidelines on colorectal cancer screening have been issued by several organizations: the ACS, the US Multi-Society Task Force on Colorectal Cancer, and the American College of Radiology, which issued a joint guideline; the USPSTF; the American College of Physicians; the American College of Gastroenterology; and the National Comprehensive Cancer Network.
All guidelines recommend routine screening for colorectal cancer and adenomatous polyps in asymptomatic adults beginning at age 50, but they differ with respect to frequency of screening, age at which to discontinue screening, and preferred screening method. Recommendations also differ for persons at high risk with respect to the age at which to begin screening, as well as the frequency and method of screening.
"Earlier starting ages were recommended in the past, but in the mid-1990s, most organizations settled on the age of 50 as a sensible starting age, and that starting age has been in place for the past 20 years," said Smith. "Will it be problematic? No question that there are initial challenges, including raising awareness in the public and healthcare professionals and advocating that health plans make screening available beginning at age 45."
Smith cautioned that this change should not be viewed as representing a conflict between the ACS and the USPSTF, because this latest recommendation comes about 2 years after the last USPSTF guideline update. "We each used modeling evidence from the same group of modelers," he said, adding that the USPSTF had considered whether to lower the starting age to 45 but elected to remain with a starting age of 50.
"In the time since their last update, the evidence supporting an earlier starting age has grown stronger," Smith explained. "This is not to suggest that they made the wrong decision and we made the right decision, but as you might expect, if two organizations have 5-year update cycles, then, going forward, the newest, different guideline simply may be based on newer data."
The data regarding a birth cohort's contributing to a rise in incidence is clear cut, he added. "Modifying the models to reflect the evidence that this incidence rate increases are carrying forward made a much stronger case for starting screening earlier," he said.
Increasing Rates in Younger Populations
Although the incidence of colorectal cancer has been steadily declining in individuals aged 55 years and older, there has been a 51% increase among those younger than 50 years since 1994, the ACS notes. Mortality rates in this population have also begun to rise recently, indicating that the upswing in incidence rates is not due solely to the increased use of colonoscopy.
The ACS notes that although colorectal cancer incidence rates are lower for those aged 45 to 49 years compared to those aged 50 to 54, the higher rates in the latter group are partially influenced by the fact that screening begins at age 50. Individuals in their 40s are far less likely to be screened than older patients, so the true underlying risk in this population is likely closer to the risk observed in adults aged 50 to 54 years. Studies also suggest that individuals in the younger age groups will continue to carry the higher risk forward as they age.
The USPSTF used three microsimulation models for their 2016 colorectal screening recommendations. Two of those models suggested that by initiating screening at age 45 instead of 50, with an interval of 15 years to the next screening, there was a slightly more favorable balance between the benefits and burden of screening. But because the estimated additional benefit were judged to be "modest" and because this finding was not supported by one of the models, a change was not made.
For the current update, the ACS used a new modeling study that incorporated more recent studies that assessed the rising incidence trends in younger adults. The results indicated that multiple screening strategies beginning at age 45, including the use of colonoscopy at the conventional 10-year interval, yielded a more favorable benefit-to-burden ratio with more life-years gained as compared to initiating screening at age 50 years.
Experts Weigh In
Approached by Medscape Medical News for a comment, Susan J. Curry, PhD, chair of the USPSTF and interim executive vice president and provost at the University of Iowa, in Iowa City, explained that their 2016 recommendation was based on a review of the available evidence regarding the benefits and harms of colorectal cancer screening.
"At the time of the task force's review, there were limited data on screening adults younger than age 50," she said. "As such, the available evidence led to our current recommendation that adults ages 50 to 75 get screened.
"As primary care clinicians and researchers, we hope patients and their doctors will continue to have conversations about colorectal cancer screening so everyone can make informed decisions about their health," Curry continued. She explained that "the hope is that these efforts will lead to additional research that can address important evidence gaps in the science of colorectal cancer screening."
Daniel M. Labow, MD, system chief of surgical oncology at Mount Sinai Hospital and site chair of the Department of Surgery at Mount Sinai St. Luke's and Mount Sinai West, in New York City, also commented on the new guidelines. "The rationale is that screening is working for the over-50 population, where the disease is more prevalent," he said. "We are seeing decreasing mortality and earlier detection of polyps. Even though the overall risk of cancer is lower in the 45 to 50 age group, by moving the age of screening back to 45, we will be able to pick up cancers in those who are just outside of standard screening cutoff."
Labow pointed out that invariably, the question comes up about lowering the screening age even further. "If we're moving it to 45, people may ask why not start screening at a younger age, like 30 years old. But given the data we have now, that would probably lead to more harm than benefit, given the very low incidence in that population."
Labow believes that overall, changing the guideline is a good move. "It is cautiously moving the age back by 5 years, and over time, data will be gathered to see its effect on mortality and detection."
The ACS receives partial funding from the Centers for Disease Control and Prevention to support the National Colorectal Cancer Roundtable, of which Dr Smith is the co-chair. Several coauthors have disclosed relationships with industry.