Even more colorectal cancer cases are being found in adults under 50, and a new collection of research suggests that a surge in screening may be tied to many of the more recent diagnoses – but not the overall trend.
In 2018, the American Cancer Society updated its guidelines for colon and rectal cancer screening, recommending that adults at average risk get screened starting at age 45 – earlier than 50, which was previously advised.
Then, in 2021, the US Preventive Services Task force also lowered the recommended age to start screening for colon and rectal cancers from 50 to 45.
The shift in screening guidelines is associated with a recent increase in early-stage colorectal cancer diagnoses, but it does not explain the rise among younger adults in general – a trend that began in the mid-1990s and includes late-stage cancers, as well. Colorectal cancer refers to colon cancer, which starts in the colon, and rectal cancer, which starts in the rectum.
“The drivers of rising incidence are still unknown, but many research efforts are ongoing, with investigations covering the gamut from microplastics to ultra processed food and many other gut exposures introduced in the last half of the 20th century, when this began,” Elizabeth Schafer, associate scientist of surveillance and health equity science at the American Cancer Society, said in an email.
Lowering the screening age “has likely facilitated earlier detection of cancers that might have been missed,” but there is still more work to do to identify the driving factors behind the ongoing overall rise of colorectal cancer in younger ages, Dr. Joseph Rinaldi, a gastroenterologist at Montefiore Einstein Comprehensive Cancer Center, said in an email.
“It is likely that factors beyond screening guidelines are contributing to the overall rise in colorectal cancer incidence,” Rinaldi said. “Much work remains to identify causal factors – whether environmental, genetic, or population-based – that can be targeted for prevention and, potentially, reversal of this trend.”
Now, research conducted by the American Cancer Society that was published Monday in the medical journal JAMA found that the share of US adults ages 45 to 49 who are up to date on colorectal cancer screening climbed from 20.8% in 2019 and 19.7% in 2021 to 33.7% in 2023.
“We’ve been waiting for screening to take off in this age group,” Schafer, an author on the new screening study, said in the email. “But the real thrill is the translation to early diagnosis, which means less intense treatment and lives saved.”
A second study, also conducted by the American Cancer Society and published Monday in JAMA, found that the prevalence of early-stage colorectal cancer diagnoses among adults 45 to 49 increased from 9.4 cases per 100,000 people in 2019 to 11.7 per 100,000 in 2021 and then to 17.5 per 100,000 in 2022.
That translates to a 50% relative increase between 2021 and 2022.
“If screening was the cause of the rise, the increase would have been for early- instead of late-stage disease,” said Schafer, lead author of the second paper.
“Local stage diagnosis was rare in this age group before screening because there are usually no symptoms yet,” Schafer said of early-stage cancers that have not spread to other parts of the body. “So yes, it was a bit shocking, actually, to see early-stage incidence double from 9.4 to 17.5 per 100,000 in this newly screened group.”
As a rise in colon and rectal cancers persists among younger adults, public health experts now urge them to know the warning signs and to get screened when eligible.
The signs and symptoms to watch for
More than half of the people who are diagnosed with colorectal cancer before 50 are not eligible for screening because they haven’t yet reached the recommended age of 45. And most people who are eligible have still not been screened, said Jessica Star, associate scientist of cancer risk factors and screening surveillance research at the American Cancer Society, who was lead author on the new screening study and an author on the other paper.
Whether someone is recommended for screening or not, they should still watch for signs and symptoms of colorectal cancer and talk with their doctor if they notice any, she said.
In the United States, about 1 in 23 men and 1 in 25 women will be diagnosed with colorectal cancer in their lifetime.
The most common symptom is rectal bleeding,” Star said in an email, adding that 41% of patients under 50 tend to experience this symptom, compared with 26% of patients older than 50. Many people also may have abdominal cramping or pain.
“Young people, especially, are reluctant to talk about these types of symptoms, but it could actually save their life,” Star said.
“Other important symptoms include a persistent change in bowel habits or the shape of stool, decreased appetite, and weight loss. People with any of these symptoms that persist for several weeks should be followed up with a doctor’s visit,” she said. “If you are young and your concerns are not being addressed, get a second opinion. There are too many stories about young people being told they have hemorrhoids, finding out months or years later that it is cancer.”
When Kelly Spill, 33, experienced symptoms of colorectal cancer after the birth of her first child, she said, her doctors told her that they were tied to being postpartum and internal hemorrhoids.
“One day I went to the bathroom, and I looked down, and you would have thought it was my time of the month, and it most certainly was not. That’s when it became extremely alarming,” Spill told CNN in May of the blood in her stool.
When she noticed massive amounts of blood again, she took photos and showed them to a primary care physician. The doctor immediately ordered a colonoscopy, and that’s what led to her being diagnosed with stage III rectal cancer at age 28 in 2020.
“To self-advocate is such a big one,” Spill said. “If I didn’t push, push, push, I don’t know where I would be, and especially as a new mom.”
Spill was treated with an immunotherapy drug called dostarlimab and is now a healthy mother of three. She remains cancer-free.
Getting screened can help reduce the risk of colorectal cancer, because almost all colorectal cancers begin as precancerous polyps in the colon or rectum. But through screening, these polyps can be identified and removed before they turn cancerous.
Current options for colorectal cancer screening for people at average risk include a stool-based fecal test either annually or every three years; a traditional colonoscopy every 10 years; a virtual colonoscopy every five years; or a sigmoidoscopy procedure, which involves using a tube-like instrument called an endoscope to examine the lower part of the colon, every five years.
A separate study published Monday in JAMA found that when people newly eligible for screening were automatically mailed a fecal test kit at their home address without asking for it, they were more likely to complete screening than those who were asked to actively choose between a colonoscopy, a fecal test or deferring screening altogether.
“Another important question is how to get more people screened, especially people without access to healthcare, a group that had no significant increase in screening in our study,” Schafer, who was not involved in that study, said in the email.
Despite recent increases in screening, it’s still estimated that more than 1 in 3 adults 45 and older are not getting screened as recommended, according to the National Colorectal Cancer Roundtable.
There are other steps people can take to help prevent colorectal cancer.
“There are many things people of all ages can do to reduce their risk, including not smoking, maintaining a healthy body weight, being physically active, avoiding excessive alcohol consumption, and eating a healthy diet that is low in red and processed meat and high in whole grains, fruits, and vegetables,” Star said.
More than half of all colorectal cancers in the US are attributable to those modifiable risk factors, according to the American Cancer Society.
“There have been several studies that work to identify factors contributing to the development of colon cancer. Maintaining a physically active lifestyle and a healthy weight is important, as obesity has been linked to early-onset disease,” Rinaldi said. “I also encourage avoiding tobacco, refined grains, and sugary beverages and instead focus on consuming a fiber-rich diet that is more plant-based and that limits the consumption of red and processed meats, as this is thought to be protective to colon health.”
