Why are colorectal, other GI cancers on the rise in younger people?

Medical News Today

09-07-2025

Increasing age is the greatest risk factor for all types of cancer, with most cases being diagnosed in people over the age of 60.However, in people under 50, there has been a rapid, worldwide increase in cancers of the digestive system, or gastrointestinal cancers.Although still far less common than in older people, early-onset colorectal cancer is now the leading cause of cancer-related deaths in men, and the second in women, in the United States.The exact cause is unknown, but the authors of a new review published in the British Journal of Surgery suggest that obesity, a Western-style diet, nonalcoholic fatty liver disease, smoking, excessive alcohol use, and even exposure to microplastics, may all be contributing to the rise.Another study, published in Nature Medicine, has further estimated that, without early intervention, as many as 15.6 million gastric cancer cases may occur in the next few decades, most of which, are attributable to infection with a common bacterium, Helicobacter pylori.The risk of all types of cancer increases with age, with, according to the National Institutes of Health, more than 1 in every 100 people over the age of 60 being diagnosed with cancer.However, in recent years, there has been a worrying increase in cancers of the digestive system — known as gastrointestinal or GI cancers — in people under the age of 50, and experts have yet to identify a reason.A new analysis of studies notes that between 2010 and 2019 early-onset colorectal cancers increased by 14.8% in the United States, and rates are increasing worldwide.The comprehensive review, which is published in The British Journal of Surgery, suggests that, while the exact cause is unknown, environmental factors, diet and lifestyle, may be responsible for the increase.Anton Bilchik, MD, PhD, surgical oncologist, chief of medicine and Director of the Gastrointestinal and Hepatobiliary Program at Providence Saint John's Cancer Institute in Santa Monica, CA, not involved in the review, suggested some possible reasons for the rise in early-onset GI cancers.'While the increase in obesity is associated with a major increase in early-onset colorectal cancer, the majority of patients are not obese, do not have a family history or any other obvious risk factors,' Bilchik told Medical News Today.'This suggests that other factors such as the environment, lifestyle, diet (processed food and red meat), lack of exercise and stress may all negatively affect the trillions of bacteria in our bodies (the microbiome) as well as our immune system creating a proinflammatory response which has been linked to the development of early onset cancers.' – Anton Bilchik, MD, PhDGreatest rises in colon and rectal cancersThe researchers note that early-onset cancers of the colon and rectum had increased the most. People born in 1990 are more than twice as likely to develop colon cancer, and more than four times as likely to develop cancer of the rectum than those born in 1950.They identified global increases in colorectal cancers. A study of 20 European countries showed that between 2004 and 2016, colorectal cancers had increased by almost 8% for those aged 20–29, almost 5% for people aged 30–39, and by 1.6% in the 40–49 age band. Even more shocking are figures from the Centers for Disease Control and Prevention (CDC) Wonder database in the U.S., which identified a 333% increase in the incidence of colorectal cancers among 15-19 year olds and a 185% increase among people aged between 20 and 24. Despite these apparently huge percentage increases, the authors emphasize that the absolute numbers of cancer diagnoses are still very much lower in those under 50 than in older people.However, the researchers on this study highlight the need for targeted awareness and interventions, particularly among younger age groups.Bilchik concurred, commenting that: 'Public awareness that GI cancer is now the leading cause of [cancer-related] deaths in males under age 50 and the second leading cause in women is essential. The US Preventative Task Force has already reduced the screening age to 45. Given the disproportionate increase in blacks and Hispanics compared with non-Hispanic whites, the screening age may need to be further reduced to 40.'Can experts explain the increase in colorectal cancers?'Though the rates of colorectal cancer are rising fastest in the youngest age groups — ages 15-24 — the absolute number of cases in this age group is relatively low compared to those aged 40-49, which makes it challenging to isolate risk factors specific to this younger group,' joint first author of the review Sara K. Char, MD, Clinical Oncology Fellow at the Dana Farber Cancer Institute, Mass General Brigham Hospital, told MNT. 'Several factors, including obesity, excessive alcohol intake, intake of a Western-pattern diet, sedentary lifestyle, and consuming sugar-sweetened beverages have been associated with increased risk of early-onset colorectal cancer,' Char suggested.'Other factors, such as exposure to microplastics and changes in the gut microbiome have also been implicated,' she told us. 'However, we know that not all patients with early-onset colorectal cancer have these risk factors. Ongoing research efforts are needed to better understand these rising trends.' Gastric cancers preventable by stopping bacterial infectionAnother recent study, led by researchers from the International Agency for Research on Cancer of the World Health Organization (WHO) in Lyon, France, and published in Nature Medicinearound the same time as the comprehensive review, found a link between gastric cancers and infections with a common bacterium.The study was concerned with preventable gastric cancers, and it analyzed data from participant cohorts across 185 countries, focusing on individuals born in 2008–2017.The researchers concluded that an estimated 15.6 million gastric cancer cases are likely to develop among people from these birth cohorts.Of these cases, a staggering 76% are attributable to infections with the bacterium Helicobacter pylori, which are very common but also preventable.This, according to the study authors, highlights the need of implementing education and preventive strategies addressing this cause for gastric cancer worldwide.What can be done to prevent colorectal cancers?While the reason for the rise in colorectal cancer cases are less clear, experts argue that perhaps, for now, the focus should be on early detection, to allow more effective treatment.At the same time, Nilesh Vora, MD, a board-certified hematologist and medical oncologist and medical director of the MemorialCare Todd Cancer Institute at Long Beach Medical Center in Long Beach, CA, also not involved in the research discussed, attributed the decrease in colorectal cancers in older people to the 'widespread adoption of colonoscopies for screening.'He told MNT that: 'Finding precancerous lesions is one way to decrease the risk of colon cancers. Could this be done in younger patients? Potentially. The recommended screening age has decreased from 50 to 45, and perhaps an argument could be made to lower screening ages even further.'Still, while emphasizing that screening guidelines relate only to asymptomatic individuals and that anyone with symptoms such as blood in stool, pain, or changes in bowel habits should see their doctor, Char explained:'In the United States, individuals at average risk of colorectal cancer are recommended to start screening at age 45. However, those with a family history of colorectal cancer or precancerous colorectal polyps should start at either age 40 or 10 years prior to the age of the affected family member, whichever is sooner. It is important for younger adults to talk to their families and understand their familial risk.''Research is ongoing to determine how to tailor screening programs to even younger individuals most at risk for developing early-onset colorectal cancer,' she added.As for lifestyle changes that may help reduce a person's risk of colorectal cancer, Char advised that:'Many generally healthy behaviors can reduce one's risk of developing colorectal cancer, such as not smoking, avoiding excessive alcohol consumption, limiting red meat consumption, treating vitamin D deficiency, and staying physically active. We generally recommend 30 minutes of moderately vigorous exercise at least five times a week.'