Colorectal cancer rates in younger people have increased in recent years. More worrisome, most diagnosed cases are at an advanced stage, and researchers aren’t sure what is causing the cancers.

According to new statistics from the American Cancer Societythe proportion of colorectal cancer that occurred in people younger than 55 years doubled between 1995 and 2019, from 11% to 20%.

That means that of the approximately 1.3 million people in the US living with colorectal cancer in the United States in 2019, about 273,800 were younger than 55.

People born after 1990 (millennials and Gen Zers) are twice as likely to be diagnosed with colon cancer and four times as likely to have rectal cancer compared to people born in 1950, a 2017 study published in the Journal of the National Cancer Institute found.

The numbers are rising at an alarming rate. TO study published in 2021, in JAMA, estimated that in just seven years, colorectal cancer will be the leading cause of cancer deaths in people ages 20 to 49.

“This is in stark contrast to people age 50 and older, who are eligible for screening, where rates and deaths from colorectal cancer have been steadily declining for many decades,” said Dr. Kimmie Ng, director of the Young Colorectal Cancer Center. -Onset. at the Dana Farber Cancer Institute, she said in an interview.

The new statistics also showed that late-stage diagnoses are rising rapidly in all colorectal cases in the US, rising from 52% in the mid-2000s to 60% in 2019.

Most of the cases diagnosed in younger people are advanced-stage cancers, Ng said. Advanced or stage 4 cancer It is often a cancer that cannot be cured or does not go away completely with treatment, but sometimes it can be controlled.

“This type of cancer is particularly asymptomatic and can remain that way for a long time,” said Dr. Folasade P. May, associate professor of medicine in the Vatche and Tamar Manoukian Division of Digestive Diseases at the University of California, Los Angeles. the tumor can grow and grow and even spread before there are symptoms that cause someone to seek medical attention.”

Many young adults are not yet aware that colorectal cancer can happen to them, which can lead them to pass off early symptoms as something else, May said.

Misdiagnosis has been found to be common among young people with colon cancer, previous research suggests.

“When I was training in medicine, I was taught that this was a disease of older people, specifically a disease of older men,” May said. “We know that now it is affecting people in the prime of their lives.”

Why is colon cancer increasing in younger people?

Known lifestyle risk factors, including higher rates of obesity, younger people living more sedentary lifestyles than before, and eating diets high in sugars and processed foods are likely contributing to the rebound.

«It’s not just about diet and lifestyle, there’s something else,» Ng said in an interview. “We see so many young colorectal cancer patients who follow very healthy lifestyles and diets.”

New data shows that the highest rates of colorectal cancer diagnoses are being diagnosed in:

  • Alaska Natives (88.5 per 100,000)
  • Native Americans (46.0 per 100,000)
  • Black Americans (41.7 per 100,000).

From 2010 to 2019, the colorectal cancer incidence rate increased in all racial and ethnic groups in the US.

Genetics, including a family history of Lynch syndrome or polyps, play a role in a person’s risk of colorectal cancer, but it only accounts for about 25% of cases in young people, according to Phillip Daschner, director of the immunology program. Cancer, Hematology, and Etiology Branch of the Division of Cancer Biology of the National Cancer Institute.

“The other 75% of these cases fall into this category of unknown cause,” he said.

The driver is undoubtedly a combination of environmental factors, May said.

«When something affects people who have their birth years in common, then we know it’s something in the environment that has led to this whole group of people having higher rates,» he said.

The phenomenon is called the birth cohort effect.

It’s not yet clear what environmental factors are at play beyond lifestyle and diet, but researchers are looking at everything from antibiotics to plastics to stress as possible culprits. It is also possible that there is an environmental toxin that has not yet been linked to colorectal cancer.

“The bottom line is that we don’t know why this is happening,” Daschner said.

When should I be examined for colon cancer?

Colorectal cancer is still rare among people under 50, but the recommended age at which a person should start projection it was reduced in 2021 from 50 to 45.

Since the adjustment occurred in the past two years, the increase in cases among people under 55 cannot be attributed to increased detection, Ng said. The fact that more cases are being found in advanced stages also rules out that the increase in detection is the cause of the increase in diagnoses.

“If it was just a detection effect, we would expect more localized cases to be diagnosed. But unfortunately that’s not what we’re seeing,” Ng said.

About 40% of early-onset colorectal cancers are diagnosed in people ages 45 to 49. The reduced screening age will be able to detect cancers in this group of people. However, cases that are increasingly being diagnosed in people in their 20s and 30s are likely to go undetected until symptoms develop.

“Research on what are the underlying causes and what are the risk factors is very important. We need to identify youth who are at high risk and select them for earlier screening,” Ng said.

Colon Cancer Symptoms

The most common symptoms of colorectal cancer include:

  • Blood in the stool
  • abdominal pain
  • unintentional weight loss
  • a change in bowel habits
  • Anemia, shortness of breath, and fatigue can also be warning signs.

Part of the problem for doctors and patients is that the symptoms can mimic other conditions, experts say. If any of the symptoms appear and do not improve, especially if someone is experiencing more than one symptom, it should be considered a warning sign.

Research suggests that if detected early while colon cancer is still localized, the five-year survival rate around 90%.