The burden of colorectal cancer in the United States is shifting to younger adults, and more patients are being diagnosed with later stage disease, according to a concerning new report from the American Cancer Society.
One in 5 new cases of colorectal cancer in the United States occur in people younger than 55 - about twice the rate in 1995, when 11 percent of cases were in this age group. In another alarming shift, 60 percent of patients are being diagnosed with an advanced stage of the disease, up from 52 percent in the mid-2000s.
The reasons behind the trends aren't fully understood, but the findings suggest that steady progress to reduce the incidence of colon cancer through screening during the past few decades is losing momentum.
"There is a bit of a worrisome trend," said Paul Oberstein, a medical oncologist at the New York University Langone Perlmutter Cancer Center who was not involved in the study. "Something is clearly different among the young, the under-50 population, that does suggest, although it's small, that the number of cancers are going up."
Overall, colorectal cancer is on the decline, largely because more people over 50 are being screened by colonoscopy, which can prevent cancer by detecting and removing premalignant polyps. Recently, the U.S. Preventive Services Task Force recommended lowering the age for colorectal cancer screen to 45.
But the new report "foreshadows less favorable trends ahead," the study authors wrote, with more patients being diagnosed at younger ages and with more advanced disease. There is also an unexplained shift in the incidence of "left-sided" tumors, suggesting that the biology of the disease could be changing, prompting a need for a new approach in prevention and more research into targeted treatments.
"We know rates are increasing in young people, but it's alarming to see how rapidly the whole patient population is shifting younger, despite shrinking numbers in the overall population," Rebecca Siegel, senior scientific director at the American Cancer Society and lead author of the report, said in a statement. "The trend toward more advanced disease in people of all ages is also surprising and should motivate everyone 45 and older to get screened."
The overall annual incidence rate of colon cancer has decreased by 46 percent, from 66.2 per 100,000 people at its peak in 1985 to 35.7 per 100,000 people in 2019. Death rates have also dropped 57 percent in the past 50 years, according to the report. Experts say the decrease in colorectal cancer cases is largely because of a drop in smoking and the wide adoption of screening for colorectal cancer in Americans age 50 or older.
But the report, based on the latest available data, through 2019, shows the gains against the disease are limited to people 65 and older. Here are some of the findings:
Colorectal cancer is the second-most common cause of cancer death in the United States. Smoking, eating processed meats, obesity and a sedentary lifestyle are all risk factors for the disease.
Arif Kamal, the chief patient officer for the American Cancer Society, said one concern is that many people ages 45 to 49 aren't getting colonoscopy screening even though they are now eligible.
"There's a clear relationship" between the rate of colonoscopies and the subsequent risk of getting cancer, he said. "The screening is also the therapy. If we see a precancerous polyp, we remove it."
Kamal said there's also some concern that people in their 40s and 50s may have less healthful lifestyles, including eating more processed foods and less fiber, than previous generations.
"As obesity rates continue to rise in the United States, we have to identify colorectal cancer as an obesity-related cancer the same way we did when we started to think about lung cancer being a smoking-related cancer," Kamal said. "It will help people see that one thing leads to another."
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