Colorectal cancer is rising among younger adults and scientists are racing to uncover why

By Jacqueline Howard, CNN

Nikki Lawson received the shock of her life at age 35.

A couple of years ago, she noticed that her stomach often felt irritable, and she would get sudden urges to use the restroom, sometimes with blood in her stool. She even went to the hospital one day when her symptoms were severe, she said, and she was told it might be a stomach ulcer before being sent home.

"That was around the time when Chadwick Boseman, the actor, passed away. I remember watching him on the news and having the same symptoms," Lawson said of the "Black Panther" star who died of colon cancer at age 43 in August 2020.

"But at that time, I was not thinking 'this is something that I'm going through,' " she said.

Instead, Lawson thought changing her diet would help. She stopped eating certain red meats and ate more fruits and vegetables. She began losing a lot of weight, which she thought was the result of her new diet.

"But then I went for a physical," Lawson said.

Her primary care physician recommended that she see a gastroenterologist immediately because she had low iron levels.

"When I went and I saw my gastro, she said, 'I'm sorry, I have bad news. We see something. We sent it off to get testing. It looks like it is cancer.' My whole world just kind of blanked out," Lawson said. "I was 35, healthy, going about my day, raising my daughter, and to get a diagnosis like this, I was just so shocked."

Lawson, who was diagnosed with stage III rectal cancer, is among a growing group of colon and rectal cancer patients in the United States who are diagnosed at a young age.

The share of colorectal cancer diagnoses among adults younger than 55 in the US has been rising since the 1990s, and no one knows why.

'Crying through chemotherapy'

Researchers at Dana-Farber Cancer Institute are calling for more work to be done to understand, prevent and treat colorectal cancer at younger ages.

In a paper published last week in the journal Science, the researchers, Dr. Marios Giannakis and Dr. Kimmie Ng, outlined a way for scientists to accelerate their investigations into the puzzling rise of colorectal cancer among younger ages, calling for more specialized research centers to focus on younger patients with the disease and for diverse populations to be included in studies on early-onset colorectal cancer.

Their hope is that this work will help improve outcomes for young colorectal cancer patients like Lawson.

Among younger adults, ages 20 to 49, colorectal cancer is estimated to become the leading cause of cancer-related deaths in the United States by 2030.

Lawson, now 36 and living in Palm Bay, Florida, with her 5-year-old daughter, is in remission and cancer-free.

The former middle school teacher had several surgeries and received radiation therapy and chemotherapy to treat her cancer. She is now being monitored closely by her doctors.

For other young people with colorectal cancer, "my words of hope would be to just stay strong. Just find that courage within yourself to say, 'You know what, I'm going to fight this.' And I just looked within myself," Lawson said.

"I also have a very supportive family system, so they were definitely there for me. But it was very emotional," she said of her cancer treatments.

"I remember crying through chemotherapy sessions and the medicine making you so weak, and my daughter was 4, and having to be strong for her," she said. "My advice to any young person: If you see symptoms or you see something's not right and you're losing a lot of weight and not really trying to, go to see a doctor."

Signs and symptoms of colorectal cancer include changes in bowel habits, rectal bleeding or blood in the stool, cramping or abdominal pain, weakness and fatigue, and weight loss.

A report released this month by the American Cancer Society shows that the proportion of colorectal cancer cases among adults younger than 55 increased from 11% in 1995 to 20% in 2019. Yet the factors driving that rise remain a mystery.

There's probably more than just one cause, said Lawson's surgeon, Dr. Steven Lee-Kong, chief of colorectal surgery at Hackensack University Medical Center in New Jersey.

He has noticed an increase in colorectal cancer patients in their 40s and 30s within his own practice. His youngest patient was 21 when she was diagnosed with rectal cancer.

"There is a phenomenon of decreasing overall colorectal cancer rates in the population in general, we think because of the increase in screening for particularly for older adults," Lee-Kong said. "But that doesn't really account for the overall increase in the number of patients younger than, say, 50 and 45 that are developing cancer."

'There's something else going on'

Some of the factors known to raise anyone's risk of colorectal cancer are having a family history of the disease, having a certain genetic mutation, drinking too much alcohol, smoking cigarettes or being obese.

"They were established as risk factors in older cohorts of patients, but they do seem to be also associated with early-onset disease, and those are things like excess body weight, lack of physical activity, high consumption of processed meat and red meat, very high alcohol consumption," said Rebecca Siegel, a cancer epidemiologist and senior scientific director of surveillance research at the American Cancer Society, who was lead author of this month's report.

"But the data don't support these specific factors as solely driving the trend," she said. "So if you have excess body weight, you are at a higher risk of colorectal cancer in your 40s than someone who is average weight. That is true. But the excess risk is pretty small. So again, that is probably not what's driving this increase, and it's another reason to think that there's something else going on."

Many people who are being diagnosed at a younger age were not obese, including some high-profile cases, such as Broadway actor Quentin Oliver Lee, who died last year at 34 after being diagnosed with stage IV colon cancer.

"Anecdotally, in conferences that I've attended, that is the word on the street: that most of these patients are very healthy. They're not obese; they're very active," Siegel said, which adds to the mystery.

"We know that excess weight increases your risk, and we know that we've had a big increase in body weight in this country," she said. "And that is contributing to more cancer for a lot of cancers and also for colorectal cancer. But does it explain this trend that we're seeing, this steep increase? No, it doesn't."

Yet scientists remain divided when it comes to just how much of a role those known risk factors -- especially obesity -- play in the rise of colorectal cancer among adults younger than 55.

Scientists debate the role of obesity

Even though the cause of the rise of colorectal cancer in younger adults is "still not very well understood," Dr. Subhankar Chakraborty argues that dietary and lifestyle factors could be playing larger roles than some would think.

"We know that smoking, alcohol, lack of physical activity, being overweight or obese, increased consumption of red meat -- so basically, dietary factors and environmental and lifestyle factors -- are likely playing a big role," said Chakraborty, a gastroenterologist with The Ohio State University Comprehensive Cancer Center.

"There are also some other factors, such as the growing incidence of inflammatory bowel disease, that may also be playing a role, and I think the biggest factors is most likely the diet, the lifestyle and the environmental factors," he said.

It has been difficult to pinpoint causes of the rise of cases in younger ages because, if someone has a polyp in their colon for example, it can take 10 to 15 years to develop into cancer, he says.

"During that, all the way from a polyp to the cancer stage, the person is exposed to a variety of things in their life. And to really pinpoint what is going on, we would need to follow specific individuals over time to really understand their dietary patterns, medications and weight changes," Chakraborty said. "So that makes it really hard, because of the time that cancer actually takes to develop."

Some researchers have been investigating ways in which the rise in colorectal cancer among younger adults may be connected to increases in childhood obesity in the US.

"The rise in young-onset colorectal cancer correlates with a doubling of the prevalence of childhood obesity over the last 30 years, now affecting 20% of those under age 20," Dr. William Karnes, a gastroenterologist and director of high-risk colorectal cancer services at the UCI Health Digestive Health Institute in California, said in an email.

"However, other factors may exist," he said, adding that he has noticed "an increasing frequency of being shocked" by discoveries of colorectal cancer in his younger patients.

There could be correlations between obesity in younger adults, the foods they eat and the increase in colorectal cancers for the young adult population, said Dr. Shane Dormady, a medical oncologist from El Camino Health in California who treats colorectal cancer patients.

"I think younger people are on average consuming less healthy food -- fast food, processed snacks, processed sugars -- and I think that those foods also contain higher concentrations of carcinogens and mutagens, in addition to the fact that they are very fattening," Dormady said.

"It's well-publicized that child, adolescent, young adult obesity is rampant, if not epidemic, in our country," he said. "And whenever a person is at an unhealthy weight, especially at a young age, which is when the cells are most susceptible to DNA damage, it really starts the ball rolling in the wrong direction."

Yet at the Center for Young Onset Colorectal and Gastrointestinal Cancers at Memorial Sloan Kettering Cancer Center, researchers and physicians are not seeing a definite correlation between the rise in colorectal cancer among their younger adult patients and a rise in obesity, according to Dr. Robin Mendelsohn, gastroenterologist and co-director of the center, where scientists and doctors continue to work around the clock to solve this mystery.

"When we looked at our patients, the majority were more likely to be overweight and obese, but when we compare them to a national cohort without cancer, they're actually less likely to be overweight and obese," she said. "And anecdotally, a lot of the patients that we see are young and fit and don't really fit the obesity profile."

That leaves many oncologists scratching their heads.

Growing doubt that genetics is involved

Some scientists are also exploring whether genetic mutations that can raise someone's risk for colorectal cancer have played a role in the rise of cases among younger adults -- but the majority of these patients do not have them.

Karnes, of UCI Health, said "it is unlikely" that there has been an increase in the genetic mutations that raise the risk of colorectal cancer, "although, as expected, the percentage of colorectal cancers caused by such mutations, e.g., Lynch syndrome, is more common in people with young-onset colorectal cancer."

Lynch syndrome is the most common cause of hereditary colorectal cancer, causing about 4,200 cases in the US per year. People with Lynch syndrome are more likely to get cancers at a younger age, before 50.

"In my practice and in the medical community, the oncologic community, I don't think there's any proof that genetic syndromes and gene mutations that patients are born with are becoming more frequent," El Camino Health's Dormady said. "I don't think the inherent frequency of those mutations is going up."

The tumors of younger colorectal cancer patients are very similar to those of older ones, said Mendelsohn at Memorial Sloan Kettering Cancer Center.

"So then, the question is, if they're biologically the same, why are we seeing this increasingly in younger people?" she said. "About 20% may have a genetic mutation, so the majority of patients do not have a family history or genetic predisposition."

Therefore, Mendelsohn added, "it's likely some kind of exposure, whether it be diet, medication, changing microbiome," that is driving the rise in colorectal cancers in younger adults.

That rise "has been something that's been on our radar, and it has been increasing since the 1990s," Mendelsohn said. "And even though it is increasing, the numbers are still small. So it's still a small population."

Better testing and diagnosing

Dormady, at El Camino Health, said he now sees more colorectal cancer patients in their early to mid-50s than he did 20 years ago, and he wonders whether it might be a result of colorectal cancer screening being easier to access and better at detecting cancers.

"The first thing to consider is that some of our diagnostic modalities are becoming better," he said, especially because there are now many at-home colorectal cancer testing kits. Also, in 2021, the US Preventive Services Task Force lowered the recommended age to start screening for colon and rectal cancers from 50 to 45.

"I think you have a subset of patients who are being screened earlier with colonoscopies; you have advancing technology where we can potentially detect tumor cell DNA in the stool sample, which is leading to earlier diagnosis. And sometimes that effect will skew statistics and make it look like the incidence is really on the rise, but deeper analysis shows you that part of that is due to earlier detection and more screening," he said. "So that could be one facet of the equation."

Overall, pinpointing what could be driving this surge in colorectal cancer diagnoses among younger ages will not only help scientists better understand cancer as a disease, it will help doctors develop personalized risk assessments for their younger patients, Ohio State University's Chakraborty said.

"Because most of the people who go on to develop colorectal cancer really have no family history -- no known family history of colon cancer -- so they would really not be aware of their risk until they begin to develop symptoms," he said.

"Having a personalized risk assessment tool that will take into account their lifestyle, their environmental factors, genetic factors -- I think if we have that, then it would allow us hopefully, in the future, to provide some personalized recommendations on when a person should be screened for colorectal cancer and what should be the modality of screening based on their risk," he said. "Younger adults tend to develop colon cancer mostly in the left side, whereas, as we get older, colon cancer tends to develop more on the right side. So there's a little difference in how we could screen younger adults versus older adults."