In a new study, researchers did a year-by-year age analysis of colorectal cancer rates among U.S. adults and found a 46% increase in new diagnoses from ages 49 to 50.
This shows that many latent cases of the disease are likely going undiagnosed until routine screenings begin at 50.
The research was conducted by a team at Tulane University School of Medicine.
Colorectal cancer is the second leading cause of cancer deaths in the United States.
As rates for younger adults continue to rise, there is considerable debate about whether to lower the age for recommended screenings.
In 2018, the American Cancer Society called for routine screenings to start at 45.
However, the U.S. Preventive Services Task Force, which sets federal screenings standards, currently recommends average-risk screening begin at age 50.
Those against beginning screenings at age 45 have argued that incidence rates in those aged 45 to 49 years have been considered relatively low compared to those aged 50 to 54 years.
The team suspected the risks for those in their mid-to-late 40s are underestimated because incident data for those age ranges would likely only include cases caught because they presented symptoms and/or have a family history of cancer, in contrast to those 50 and older who have cancers also detected due to screening.
In the study, they examined colorectal cancer incidence rates in one-year increments between the ages of 30 to 60 from the year 2000 to 2015.
They suspected that if there were many asymptomatic cases of the disease undetected there would be a marked increase in cases between 49 and 50 when screenings begin.
They found that almost 93% of the cases discovered at age 50 were invasive, meaning that most would require more aggressive treatment including surgery and were likely lingering for some time before diagnosis.
The findings suggest a high case burden of preclinical, undetected early-onset colorectal cancers in patients younger than 50 that is not reflected in observed incidence rates.
The study adds fuel to the debate about whether screenings should begin at age 45.
The team says the combined burden of undetected and detected early-onset colorectal cancer cases for those 45-49 may actually approach that of individuals in their early 50s.
The lead author of the study is Dr. Jordan Karlitz, an associate clinical professor of Medicine.
The study is published in JAMA Network Open.
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