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A study using U.S. National Cancer Institute data found colorectal cancer incidence rose in 2023 after falling for more than two decades, with increases across age groups up to 65–69. The sharpest recent rise was among adults aged 45–49, but researchers say screening changes do not explain the broader pattern and the causes remain uncertain.
A study of U.S. cancer data found that colorectal cancer incidence rose in 2023 after declining for more than 20 years, with increases across age groups through 65–69. The findings, published in NEJM Evidence, show the trend is not confined to adults under 50 and could increase demand for cancer treatment and survivorship care.
Researchers led by Caitlin Murphy, a University of Chicago professor of pediatrics and public health sciences, analyzed National Cancer Institute incidence data covering two decades. The age-adjusted rate fell from 55.2 cases per 100,000 people in 2000 to 36.7 in 2022, then rose to 38.3 in 2023. The figures measure incidence, not the number of people who died from the disease.
The steepest increase was among adults aged 45–49: incidence rose by 12.76% annually from 2019 through 2023, the study authors reported. They said increased screening after national guidance lowered the recommended starting age from 50 to 45 likely contributed to the rise in this group, because screening can find cancers that otherwise would not yet have been diagnosed.
That explanation does not account for the overall increase or the changes in other age groups, the researchers said. Incidence also rose among people aged 65–69, while rates among those aged 70–74 plateaued. The authors found the increase persisted when they excluded data from 2020 and 2021, suggesting pandemic-era disruptions alone do not explain the 2023 result.
A Trend Beyond Younger Adults
The results broaden concern from early-onset colorectal cancer to a pattern that includes older adults. Colorectal cancer is the second-leading cause of cancer-related deaths overall in the United States and ranks first among adults younger than 50, according to the UChicago Medicine report. Increasing diagnoses across several age groups could place added demands on screening services, treatment and long-term follow-up care.
The study does not establish why incidence is rising. Murphy described the possibility of a birth-cohort effect: people born in the 1960s and later may carry risks that become apparent as they age. If a rise continues as these groups move through older adulthood, the number of people needing care could grow. That is a concern raised by the researchers, not a forecast quantified by this study.
Screening remains a way to find cancer early and, in some cases, prevent it. The report says average-risk adults are advised to begin regular screening at 45 and continue through 75. Choices and timing outside those ages should be discussed with a clinician, taking personal circumstances into account.
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From a Long Decline to an Increase
For decades, U.S. colorectal cancer incidence had generally declined. The new study identifies a reversal in the latest data: after the age-adjusted rate reached 36.7 per 100,000 in 2022, it increased to 38.3 in 2023. Murphy called it the first rise in the overall rate in more than 20 years, as quoted by UChicago Medicine.
Attention in recent years has focused on younger adults. American Cancer Society statistics cited in the report show incidence among adults aged 20–49 rose by 3% annually from 2013 to 2022. The new analysis extends the concern to age groups beyond those traditionally described as having early-onset disease. It also highlights an important distinction: the jump among 45–49-year-olds may partly reflect more screening, while that change does not explain the broader increase.
The study authors examined whether missed screening and diagnoses during the COVID-19 pandemic could account for the later rise. They reported that the increase remained when 2020–2021 data were removed, and said screening had largely returned to pre-pandemic levels by January 2021. These findings make pandemic disruption an unlikely explanation for the increase observed in 2023, but do not identify the cause.
““This is the first time that we have seen an increase in the overall rate since in more than 20 years.””
— Caitlin Murphy, University of Chicago professor and study author, as quoted by UChicago Medicine
Causes of the Increase Remain Unknown
The study shows changes in recorded incidence, but it does not determine which exposures or behaviors are driving the increase. Researchers said screening likely contributed to the rise in diagnoses among people aged 45–49; it does not explain the overall pattern or the increases in other age groups. The reported rates also cannot, by themselves, distinguish a change in underlying disease risk from changes in detection for every group.
Murphy and colleagues are investigating environmental chemical exposures as one possible area of research. The team plans to measure many exposures in blood samples and then study chemicals of interest using colon organoids, laboratory models grown to represent colon tissue. The source report does not identify a specific chemical as a cause.
The analysis covers data through 2023, so it cannot establish whether the increase continued in later years. Researchers also have not quantified how much additional treatment or survivorship care would be required if the trend persists. Those questions depend on future incidence data and further research.
More Data and Risk Research
Cancer registry figures are updated annually, and the study authors call for continued surveillance to see whether the increase persists. Newer data can help show whether the 2023 change represents a continuing trend and how rates develop across age groups.
The research team plans to investigate possible environmental exposures through blood testing and follow-up laboratory work with colon organoids. Those studies may help identify candidates for further investigation, but the report does not say when results will be available or whether any exposure will be shown to affect cancer risk.
For screening, the report says average-risk adults should follow national recommendations to begin at age 45 and continue through 75. People with a family history, inherited risk, symptoms or other relevant health concerns may need individualized guidance. A qualified clinician can discuss which screening test is appropriate and how often it should be repeated.
Key Questions
What did the study find?
Using U.S. National Cancer Institute data, the researchers found the age-adjusted colorectal cancer incidence rate rose from 36.7 per 100,000 in 2022 to 38.3 in 2023, after falling for more than two decades. Rates increased across age groups through 65–69.
Which age group had the sharpest increase?
Adults aged 45–49 had the steepest reported rise: incidence increased by 12.76% annually from 2019 to 2023. The authors said increased screening after the recommended starting age was lowered to 45 likely contributed to this group’s rise.
Do researchers know what is causing the increase?
No. The study identifies a trend but does not establish its cause. Researchers are investigating possible factors, including environmental chemical exposures, but no specific exposure has been confirmed as responsible.
Does the study mean screening caused cancer rates to rise?
No. More screening can lead to more cancers being detected, which may help explain the increase among 45–49-year-olds. The authors said this does not explain the overall increase or the changes in other age groups.
When should average-risk adults be screened?
The report says national guidance recommends regular screening for average-risk adults from ages 45 through 75. Screening decisions for people outside those ages, or with personal risk factors or symptoms, should be discussed with a qualified clinician.
Source: uchicagomedicine.org
