Nearly half of all new colorectal cancer cases now occur in adults under 65, signaling a major shift in the demographics of the disease, according to new data published Monday by the American Cancer Society.
“This was always a disease that was Grandpa’s disease,” said Dr. William Dahut, chief scientific officer of the American Cancer Society. But among people 65 and older, colorectal cancer rates have been steadily declining since the mid-1980s, thanks in large part to widespread screening that can catch precancerous polyps and early-stage cancers.
By contrast, studies in recent years have shown colorectal cancer rates on the rise among adults under 50. The new paper showed that rates among adults ages 50 to 64 also increased between 2013 and 2022 and that rates of rectal cancer in particular climbed among all ages combined after years of decline.
Researchers have observed what’s called a “birth-cohort effect” with colorectal cancers, meaning that successive generations — in this case, beginning with those born in the 1950s — are showing progressively increased risk. People born in 1990 are twice as likely as those born in 1950 to develop colon cancer, and four times as likely to develop rectal cancer.
“This isn’t necessarily an age-specific thing — this is a generational thing,” said Andreana Holowatyj, an assistant professor of hematology and oncology at Vanderbilt University Medical Center in Tennessee who wasn’t involved in the study.
The study also found that the new cases were driven largely by cancers of the far side of the colon and the rectum, rather than cancers in other parts of the colon, which are more common among older adults.
The distinct location of the cancers and the rising rates suggest that there may be unique drivers of the disease in younger generations. For example, scientists suspect environmental exposures that began around the 1950s may be partially responsible. Much of the ongoing research is focused on changes to the gut biome and inflammation associated with modern products like ultraprocessed foods, microplastics and antibiotics, the study said.
The new findings also have important implications for identifying and treating these cancers, experts said.
What should younger people look out for?
Doctors recommend routine screening starting at age 45 for people who are at average risk of colorectal cancer. A colonoscopy is considered the gold standard for screening.
People who have a family history of colon cancer or of precancerous polyps, particularly before age 60, are considered to be above-average risk. The general rule of thumb for these people is to begin screening a decade before the earliest age at which a family member had a polyp or cancer, Dr. Dahut said, but people with such a history should consult their doctor.
The new study found that three out of four adults under 50 were diagnosed at Stage 3 or 4, partly because they were not routinely screened and also because it often takes longer for younger people to receive an accurate diagnosis. Dr. Andrea Cercek, co-director of the Center for Young Onset Colorectal and Gastrointestinal Cancer at Memorial Sloan Kettering Cancer Center in New York, said her patients often had anemia or abdominal pain, both symptoms of colorectal cancers, that was initially blamed on other causes, like heavy periods or inflammatory bowel disease.
Because people under 45 aren’t routinely screened, experts say it’s particularly important for them to pay attention to potential symptoms, which can also include fatigue, unexplained weight loss, diarrhea, constipation, blood in the stool or other changes to bowel habits.
How are colorectal cancers treated?
People diagnosed with nonmetastatic colon cancer typically have surgery, which may be followed by chemotherapy, Dr. Cercek said. Colon cancer doesn’t commonly require radiation.
People with nonmetastatic rectal cancer usually receive chemotherapy and radiation before proceeding to surgery, Dr. Cercek said. The radiation in particular can have damaging and lasting consequences for male and female fertility, said Dr. Holowatyj. About 30 percent of patients who undergo rectal cancer surgery will also need a permanent ostomy, an opening that reroutes stool to an external pouch, Dr. Cercek said. Even those who don’t can face a lifetime of bowel issues resulting from surgery.
For this reason, researchers like Dr. Cercek are looking for new ways to avoid surgery as treatment. For example, research has found that some colorectal tumors with specific mutations can respond well to immunotherapy alone.
What’s the prognosis for rectal cancer? Or colon cancer?
Rectal and colon cancer have similar long-term survival rates. The most important factor for both is the stage at diagnosis. Among patients diagnosed with cancer that had not spread beyond a local area, 91 percent survived five years, compared with 15 percent of patients diagnosed with cancers that had spread to distant organs or tissues.
Despite being more commonly diagnosed at later stages, younger people had similar or higher survival rates than older people, the study found. In part, that was because they were healthier to begin with and were more physically active after treatment. “Stage for stage, young people will do better,” Dr. Dahut said.
Nina Agrawal is a Times health reporter.
The post Nearly Half of Colorectal Cancers Now Occur in Younger Patients, Study Shows appeared first on New York Times.
