Seattle scientists seek answers as colorectal cancer trends younger

Bekah Kooy's fatigue came in waves. She was often exhausted, sometimes too tired to exercise or get through the day without a nap.

She mostly chalked it up to being a new mom. In 2023, she had three young children - a 7-year-old and 4-year-old twins - and was working full time as a general surgery physician assistant.

Then one afternoon after lunch, nausea washed over her. She thought it was food poisoning at first, but the discomfort persisted. Within two days, Kooy was in so much pain she could barely move.

Co-workers pushed her to visit the emergency department, where a CT scan showed a mass obstructing her right colon. Kooy quickly understood that it was colon cancer.

She was 38, otherwise healthy and with no family history or genetic predisposition to the disease.

"I don't carry any of those markers that predispose me to colon cancer," Kooy said. "Why did this happen to me?"

The question is currently one of intense study among gastrointestinal doctors and scientists in the U.S., who are puzzled at the rise of colorectal cancer among younger adults over the last couple of decades. Once a disease thought to only affect older people, colorectal cancer has now become the leading cause of cancer-related deaths among adults under 50, despite declining overall rates, according to the Cancer Research Institute.

In Washington, colorectal cancer rates among people ages 20 to 49 increased about 16% between 2020 and 2023, according to the state Department of Health. In 2023, 595 adults in that age group were diagnosed with colorectal cancer, of about 3,400 total cases, according to the state's most recent available data.

Experts often point to diet, physical inactivity, smoking and alcohol use as possible reasons for the uptick, but also say a lot remains unknown about why the disease is trending younger.

In Seattle, scientists are contributing to the unfolding research by studying other potential, more complex risk factors, such as how exposures in the environment might be interacting differently with people's intestinal tracts and somehow leading to precancerous polyps.

"Our genetics hasn't changed as a species, so there must be some environmental reasons," said Dr. Neelendu Dey, a gastroenterologist at Fred Hutchinson Cancer Center.

While researchers are homing in on risks and root causes, they're also advocating for earlier screenings and less invasive tests.

In 2021, the U.S. Preventive Services Task Force changed its colorectal cancer screening guidance to recommend that adults over 45, rather than 50, begin evaluations, following similar moves by the American Cancer Society. The American Cancer Society this year also added guidelines for a blood-based test and an at-home option that looks for hidden markers in stool samples for patients of average risk, attempting to lower barriers to access.

Colonoscopies remain the gold standard for detecting colorectal cancer and are still recommended for younger people with symptoms or family history, but because they can be time-intensive - and aren't generally covered by insurance for average-risk patients under 45 - cancer experts are pushing for other options.

"We can't just put everyone through a colonoscopy," Dey said. "There's really a need for noninvasive tests to get a better sense of one's risk."

For Kooy, who wasn't eligible for colorectal cancer screenings when she was diagnosed, the lack of early testing options was frustrating. Other challenges came with the reality of a diagnosis in her 30s, like juggling a full-time job and caring for young kids while undergoing treatment.

"The stressors are different. The consequences are different," Kooy said of younger patients. "Thinking about missing my children's entire lives. Worried about leaving your spouse to raise three children on their own."

She added, "That's potentially unique to the younger cohort of us that have gotten colon cancer."

What the science says

The answers behind why colorectal cancer is trending younger may lie in the gut microbiome.

The microbiome is the ecosystem of microbial organisms, or microbes, that interact with each other in the gut, said Dey, whose Fred Hutch lab studies how microbial communities influence gastrointestinal disease. Microbes can protect us against pathogens, help our immune system develop and allow us to digest food, but there are also "bad" microbes, Dey said.

"There are relationships that are synergistic," he said. "They can be competitive. But there's usually more of a balance that's established pretty early in life."

Once microbes digest and metabolize what we eat, they can produce byproducts that impact our health, Dey continued. Because everyone's microbiome is different, we might each have different health responses to the same environmental exposures, he explained.

So, the question is: What's happening in the gut microbiome that might make a person more likely to develop polyps that could eventually lead to cancer? And, in addition to polyps, what are other "precancer states" medical providers can identify and intervene in?

"Precancer is really at the forefront of our minds," Dey said.

One microbe that's been linked to early onset colorectal cancer is the common bacteria E. coli.

Most E. coli are harmless and part of healthy intestines, but some can make people sick. Last year, researchers at the University of California, San Diego, found evidence that colibactin, a toxin made by some E. coli strains, could put people at increased risk of developing colon cancer at a younger age. Colibactin is a bacterial toxin that can cause DNA mutations, and the study showed those mutation patterns were over three times more common in early onset cases, especially in adults under 40.

The research did not conclusively prove colibactin caused the patients to develop cancer earlier in life, however.

"It's an area of continued research and controversy, because there were also other papers that didn't necessarily have the same finding, but we do think that this organism is important in colon cancer," Dey said.

Treatment decision

Shortly after Kooy learned about the tumor in her colon, she was scheduled for surgery.

When the pathology results came back, she learned she had medullary carcinoma, a rare cancer subtype that accounts for less than 1% of patients with colon cancer (the majority of colon cancer patients have adenocarcinoma).

Her tumor also had a high tumor mutation burden, meaning a lot of DNA mutations, and was large and locally invasive, said Dr. Stacey Cohen, Kooy's oncologist. So although surgeons were able to remove her tumor and her lymph nodes returned negative, her cancer was considered to be high-risk Stage II.

"At that point, I had a decision to make," Kooy said.

Chemotherapy is common for many types of cancer, but research shows tumors with high mutation burdens respond well to immunotherapy, said Cohen, who directs Fred Hutch's colorectal cancer specialty clinic.

Envisioning fewer short- and long-term side effects, Kooy opted for immunotherapy, which activates the body's immune system to fight the cancer, instead of attacking the cancer cells directly.

Treatment was filled with its own challenges after Kooy developed significant hyperthyroidism and allergic reactions to her cancer drug. But after almost a year, her tests showed favorable results.

Last month, Kooy marked three years in remission. She's relieved and grateful.

She also continues to carry anxiety that the disease could return, feeling nerves creep back every time she goes in for follow-up blood work or imaging. And she still wonders how her cancer developed in the first place.

"It's not just one thing, most likely, that contributes to early onset cancer," said Ulrike Riki" Peters, a molecular and genetic epidemiologist at Fred Hutch who focuses on studying colorectal cancer. "There are many things that we really don't understand."

While clear risk factors include obesity and high red meat and low fiber diets, Fred Hutch researchers said, more studies are needed around others that have shifted enormously over the decades: the impact of environmental pollutants, chemicals, changes in sleep, antibiotics exposure.

"Bekah's story shows why we need to do expert-level, individualized assessments on every single patient, Cohen said.

It's taken time for Kooy to fully reflect on the experience.

She thinks about how life, for the most part, has moved on, and tries to search for lessons from the past three years, despite still not knowing the full story. She treasures her time with family and friends. She and her husband are planning a trip to London and Paris with the kids this summer.

"Cancer really makes you want to live your life," Kooy said.

In the future, she hopes screening guidelines and testing options are expanded to include more people, as well as further studies.

"We know that more people are getting diagnosed, but these changes don't just happen," she said. "And that's hard as a patient. I don't want to be the statistic nobody knows anything about."

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