The reasons behind the trends are not fully understood, but the findings suggest that steady progress in reducing the incidence of colon cancer through screening over the past few decades is losing momentum.
“There is a worrying trend,” he said Paul Oberstein, a clinical oncologist at NYU Langone Perlmutter Cancer Center who was not involved in the study. “Something is different in the younger, under-50 population, which suggests that the number of cancers, albeit small, is increasing.”
Overall, colon cancer is declining, and more people over the age of 50 are screened with colonoscopy, which can prevent cancer by detecting and removing early polyps. Recently, the US Preventive Services Task Force recommended lowering the age for colon cancer screening to 45.
But the new report “forecasts less favorable trends going forward,” the study authors wrote, with more patients diagnosed at a younger age and more advanced disease. There is also an unexplained shift in the incidence of “left-sided” tumors, suggesting that the biology of the disease may be changing, prompting the need for new approaches to prevention and more research into targeted therapies.
“We know that rates are increasing in younger people, but it’s alarming to see how quickly the entire patient population is becoming younger, even though the numbers are declining in the overall population.” Rebecca Seal, senior scientific director of the American Cancer Society and lead author of the report, said in a statement. “The trend toward more advanced disease in all age groups is surprising and should encourage everyone 45 and older to get screened.”
The overall annual incidence rate of colon cancer has decreased by 46 percent, from a peak of 66.2 per 100,000 in 1985 to 35.7 per 100,000 in 2019. Over the past 50 years, the death rate has dropped by 57 percent. Experts say that colon cancer rates are declining as colon cancer screenings become more widely accepted among Americans age 50 and older and smoking declines.
But the report, based on the latest data available through 2019, shows that gains against the disease are limited to those 65 and older. Here are some of the findings:
- In those younger than 50, the incidence rate increased by 2 percent per year.
- People under the age of 50 die from this disease. Since 2004, the death rate for this age group has increased by about 1 percent annually.
- Overall, more patients are diagnosed with regional or distant disease, meaning it has spread beyond the colon to nearby or distant lymph nodes, tissues, or organs. The incidence of regional-stage and distant-stage disease has increased by about 3 percent per year in those under 50, while rates in those 65 and older have stabilized after a decade of steep decline.
- Overall, men are more at risk than women. The incidence rate of colon cancer was 41.5 per 100,000 for men and 31.2 for women. Differences in risk factors such as unhealthy diet, smoking history and overweight may be due to differences, the report said.
- The disease disproportionately affects people of color. The incidence rate for whites was 35.7 per 100,000, compared to Native Alaskans (88.5 per 100,000), Native Americans (46 per 100,000), and blacks (41.7 per 100,000).
Oberstein said there is “very little understanding” of why colon cancer cases are increasing among young adults. But other developed countries are seeing the same trend.
Colorectal cancer is the second most common cause of cancer death in the United States. Risk factors for the disease include smoking, eating processed meat, obesity and a sedentary lifestyle.
Arif Kamal, chief patient officer of the American Cancer Society, said one concern is that many people between the ages of 45 and 49 are not getting colonoscopy screenings, even though they are now eligible.
There is a clear relationship between the rate of colonoscopies and the risk of developing cancer, he said. “Screening is also treatment. If we find a precancerous polyp, we remove it.”
Kamal said there is some concern that people in their 40s and 50s lead less healthy lifestyles than previous generations, including eating more processed foods and less fiber.
“As obesity rates continue to rise in the United States, we need to recognize colon cancer as an obesity-related cancer, just as we are starting to think about lung cancer as a smoking-related cancer,” Kamal said. “It helps people see that one thing leads to another.”
