mirroring the well-documented increases in early-onset CRC in persons younger than 50 years.
“It’s likely that the factors contributing to CRC at age 50–54 years are the same factors that contribute to early-onset CRC, which has increased in parallel,” Caitlin Murphy, PhD, MPH, with the University of Texas Health Science Center at Houston, said in an interview.
“Many studies published in just the last year show that the well-known risk factors of CRC in older adults, such as obesity or sedentary lifestyle, are risk factors of CRC in younger adults. Growing evidence also suggests that early life exposures, or exposures in childhood, infancy, or even in the womb, play an important role,” Dr. Murphy said.
The study was published online October 28 in Gastroenterology .
Dr. Murphy and colleagues examined trends in age-specific CRC incidence rates for individuals aged 45–49, 50–54, and 55–59 years using the National Cancer Institute Surveillance, Epidemiology, and End Results (SEER) program.
During the period 1992–2018, there were a total of 101,609 cases of CRC among adults aged 45–59 years.
Further analysis showed that the CRC incidence rates rose from 23.4 to 34.0 per 100,000 among people aged 45–49 years and from 46.4 to 63.8 per 100,000 among those aged 50–54 years.
Conversely, incidence rates decreased among individuals aged 55–59 years, from 81.7 to 63.7 per 100,000 persons.
“Because of this opposing trend, or decreasing rates for age 55–59 years and increasing rates for age 50–54 years, incidence rates for the two age groups were nearly identical in 2016–18,” the researchers write.
They also found a “clear pattern” of increasing CRC incidence among adults in their early 50s, supporting the hypothesis that incidence rates increase at older ages as higher-risk generations mature, the researchers note.
These data send a clear message, Dr. Murphy told this news organization.
“Don’t delay colorectal cancer screening. Encourage on-time screening by discussing screening with patients before they reach the recommended age to initiate screening. The U.S. Preventive Services Task Force now recommends initiating average-risk screening at age 45 years,” Dr. Murphy said.
Concerning but not surprising
Rebecca Siegel, MPH, scientific director of Surveillance Research at the American Cancer Society, in Atlanta, who wasn’t involved in the study, said the results are “not surprising” and mirror the results of a 2017 study that showed that the incidence of CRC was increasing among individuals aged 50–54 years, as reported.
What’s “concerning,” Ms. Siegel said, is that people in this age group “have been recommended to be screened for CRC for decades. Hopefully, because the age to begin screening has been lowered from 50 to 45 years, this uptick will eventually flatten.”
David Johnson, MD, professor of medicine and chief of gastroenterology at Eastern Virginia Medical School, in Norfolk, Va., who also wasn’t involved in the study, said the increasing incidence is “concerning in this younger population, and similar to what is seen recently for the 45- to 49-year-old population.
“Recent data have linked dietary influences in the early development of precancerous colon polyps and colon cancer. The increased ingestion of processed foods and sugary beverages, most of which contain high fructose corn syrup, is very likely involved in the pathogenesis to explain these striking epidemiologic shifts,” Dr. Johnson said in an interview.
“These concerns will likely be compounded by the COVID-related adverse effects on people [in terms of] appropriate, timely colorectal cancer screening,” Dr. Johnson added.
The study was supported by the National Cancer Institute at the National Institutes of Health. Dr. Murphy has consulted for Freenome. Ms. Siegel and Dr. Johnson have reported no relevant financial relationships.
A version of this article first appeared on Medscape.com.