Colon cancer continues to rise among younger U.S. adults, with the American Cancer Society reporting a doubling of cases in people younger than 55 in about 25 years.
Also, significantly more Americans are being diagnosed with advanced stages of the disease, the cancer society says.
As of 2019, 20% of colon cancer cases occurred in adults under age 55 — up from just 11% in 1995, according to the new report.
Moreover, researchers found that the proportion of people diagnosed with advanced-stage cancer reached 60% in 2019, up from 52% in the mid‐2000s. The rate of advanced disease was 57% in 1995 before widespread screening was available.
Cancer experts are baffled, especially since numbers are declining in the overall population.
"We don't know what is driving the increase in colorectal cancer among young people," said senior researcher Dr. Ahmedin Jemal, senior vice president for surveillance and health equity science at the cancer society.
"There is a lot of research going on. Some people say it's probably obesity or changes in diet over the past decades that might be a reason, but really, we don't know exactly what causes this rapid rise in colorectal cancer incidence rates," he said.
This year more than 153,000 Americans will be diagnosed with colon cancer and 52,550 will die from the disease, the researchers note.
Screening is the best protection against colon cancer, Jemal said.
The cancer society recommends that screening start at age 45 for people at average risk. But Jemal said only 4 in 10 adults are being screened.
"If we were to raise colorectal cancer screening up to 80%, we estimated tens of thousands of cases could be averted, and thousands of lives could be saved," he said.
Your doctor can provide you with a fecal blood test or refer you for colonoscopy screening, Jemal said. The advantage of the colonoscopy is that it needs to be done only every 10 years, while the other should be done yearly.
Barriers to screening include being uninsured and not getting a recommendation for screening from a primary doctor, he said.
Even though younger adults are developing colon cancer, Jemal doesn't anticipate the recommended age for screening will get lower.
"It is very unlikely because there will be a cost-benefit analysis and among all colorectal cancer cases that occur under age 50, 43% occur in ages 45 to 49. So it is very unlikely that it would have any benefit if we were to go to a younger age," Jemal said.
Dr. John Ricci, chief of colorectal surgery at Long Island Jewish Medical Center in Great Neck, N.Y., said he treats many younger colon cancer patients nowadays.
"Where it used to be almost unheard of to see somebody in their 30s with colon cancer, now we're seeing it fairly frequently, unfortunately," Ricci said.
Patients have to be aware of their family history, Ricci said.
"It's not only cancers in your family history, it's also high-risk polyps," he said. If close family members have had more than three polyps or big polyps, you would qualify for an early colonoscopy, Ricci said. Polyps can turn into cancers if they are not removed.
Changes in bowel habits and bleeding -- symptoms of colon cancer -- are reasons to be evaluated by your gastroenterologist. "When you have symptomatic cancer, it's usually further along," Ricci said.
Doctors need to recommend screening and patients need to be proactive and ask their doctor about screening, he added.
"You just have to be cognizant that colorectal cancer is not an old person's disease anymore," Ricci said. "It's a middle-aged people's disease now. And it seems not enough people are getting screened."
For the report, Jemal's team used data available through 2019 from 50 states and the District of Columbia from the U.S. National Cancer Institute and the U.S. Centers for Disease Control and Prevention.
They found that incidence of colon cancer and related deaths declined from 3%-4% a year during the early 2000s to 1% a year and 2% a year, respectively, in the past decade.
Colon cancer rates were 33% higher in men (41.5 per 100,000) than in women (31 per 100,000) from 2015 to 2019, likely due to differences in risk factors, such as excess body weight, eating processed meats and smoking, the researchers note.
Rates of colon cancer have declined for those 65 and older and have stabilized for people 50 to 64, but have increased by 2% yearly in people younger than 50 and those 50 to 54.
Moreover, deaths from colon cancer have increased since about 2005 by 1% a year in people younger than 50 and by nearly 1% in people 50 to 54, the researchers say.
The highest rates of colon cancer are among Alaska Natives (88.5 per 100,000), American Indians (46 per 100,000) and Black people (41.7 per 100,000). Among white people, incidence is 35.7 per 100,000. Death patterns are similar, with the highest among Alaska Natives, American Indians and Black people.
The report was published online March 1 in CA: A Cancer Journal for Clinicians.