Colorectal cancer, which has the third highest incidence in the world, is targeting young people

The general population undergoes colorectal cancer risk assessments from the age of 40

Text/ Xin Na Zhu Sihan

Editor / Wang Xiao

Photo/unsplash

Colorectal cancer is eyeing more and more young people.

Recently, a review of early-onset colorectal cancer was published in The Lancet-Gastroenterology and Hepatology, revealing a new trend in the worldwide colorectal cancer epidemic: in recent decades, although the incidence of colorectal cancer in the elderly population has remained stable or declining, more and more people under the age of 50 are beginning to develop, a condition known as early-onset colorectal cancer.

Previously, colorectal cancer was once considered a disease of old age, and the risk of developing it increases with age. And compared with late-onset colorectal cancer, patients with early-onset colorectal cancer are often diagnosed with a progressionary period.

In response, several countries have updated their guidelines to recommend that the age of initiation for colorectal cancer screening in general-risk populations be reduced from 50 to 45 years. In China, the recommendation from the 2020 China Guidelines for Screening for Colorectal Cancer and Early Diagnosis and Early Treatment is that the general population undergoes a colorectal cancer risk assessment from the age of 40, and those assessed as low- and medium-risk and high-risk are screened for colorectal cancer from the age of 50 and 40, respectively.

The incidence of early-onset colorectal cancer is on the rise

In China, colorectal cancer has long been recognized as one of the most common malignant tumors that seriously impair health and longevity, and has become one of the three major malignant tumors that threaten life and health.

Colorectal cancer is a cancer that initially develops in the colon or rectum. According to the latest global cancer burden data released by the World Health Organization's International Agency for Research on Cancer (IARC) in 2020, colorectal cancer currently ranks third in the global incidence spectrum and second in the cause of death spectrum, accounting for 10% and 9.4% of the total number of cancer incidence and death, respectively.

According to data released by IARC, there were about 560,000 new cases of colorectal cancer in China in 2020, resulting in nearly 300,000 deaths. Data from the World Bank's IHME-GBD shows that colorectal cancer in China already accounts for 31% of the world's patients.

The new trend now discovered by researchers is that the incidence of early-onset colorectal cancer is on the rise and has become a major issue in the field of public health.

As mentioned in the above review article in The Lancet-Gastroenterology and Hepatology, the global incidence of early-onset colorectal cancer has increased over the past few decades. According to cancer registry data from 20 European countries and territories: the incidence of colon cancer among people aged 20-29 years rose from 0.8 per 100,000 in 1990 to 2.3 per 100,000 in 2016.

Among people aged 30-39 years, the incidence rose from 2.8 per 100,000 in 2006 to 6.4 per 100,000 in 2016, respectively, and in people aged 40 to 49 years, the incidence rose from 15.5 per 100,000 in 2005 to 19.2 per 100,000 in 2016. Not only in Europe, researchers have also found an increasing trend in the incidence of early-onset colorectal cancer in several countries in North America, Oceania and Asia.

In China, the incidence of early-onset colorectal cancer is 6.4 per 100,000 people, with an annual percentage change of 0.4%.

In January 2022, a new study published in Gastroenterology, the top journal in gastroenterology, also supported this trend. The research team analyzed a dataset of nearly 3 million outpatient colonoscopy patients, and during the 2014-2020 study period, more than 2.92 million colonoscopies were recorded, and more than 560,000 were first-time examinations. Among them, more than 140,000 cases occurred in people aged 18-44 years; nearly 80,000 cases occurred in people aged 45-49 years; and more than 330,000 cases occurred in people aged 50-54 years.

The nationally representative study of patients under the age of 50 in the United States suggested that the incidence of colorectal tumors and advanced precancerous lesions (APL) in people aged 45 to 49 years was almost as high as that in people aged 50 to 54 years, and the incidence of colorectal cancer was even higher.

In people aged 40 to 44 years, the incidence of APL is almost as high as that of people aged 45 to 49 years, and the incidence of colorectal cancer is also quite high. It is also worth noting that even in people aged 30-39 years, 15%-20% already have tumors, of which 2%-4% have APL and 0.2%-0.4% have colorectal tumors.

Obesity and sugar may be triggers

At present, researchers are unable to explain the precise causes of the high incidence of early-onset colorectal cancer, but the results of existing studies are suggesting several high-risk triggers.

Another article on early-onset colorectal cancer, published in The Lancet-Gastroenterology and Hepatology, mentions that the available data show a cohort effect, with an increased risk of early-onset colorectal cancer in people born after the 1960s compared to previous generations.

This finding suggests that the reasons for the increased risk of early-onset colorectal cancer may be analyzed from the common risk factors of this generation. Trends such as obesity, sedentary lifestyles, Westernization of diets, and increased antibiotic use in early childhood and antibiotic use in the food chain are possible causes of an increased risk of disease.

A growing body of research is also beginning to support the relationship between obesity and sugar intake and colon cancer. In November 2021, a study led by Washington University School of Medicine in St. Louis, published online in the journal Gut, found a link between drinking sugary drinks (SSBs) and an increased risk of colorectal cancer in women under the age of 50. The findings suggest that consuming large amounts of sugary drinks (13 to 18 years of age) during adolescence and adulthood increases the risk of colorectal cancer.

Sugary beverages such as soft drinks, fruit drinks, sports drinks, and energy drinks are the main sources of added sugar to the U.S. diet. Of nearly 117,000 participants, the researchers identified a diagnosis of 109 cases of early-onset colorectal cancer.

Women who drank ≥ 2 servings a day more than doubled their risk of early-onset colorectal cancer compared to those who drank more than one serving a week in adulthood. Increasing one serving per day increases the risk by 16%.

At ages 13 to 18, the risk of early-onset colorectal cancer increases by 32% for each additional SSB intake per serving/day. Replacing SSB intake per serving/day in adulthood with artificial sweetened beverages, coffee, reduced milk, or whole milk was associated with a 17% to 36% lower risk of early-onset colorectal cancer.

Another suggestive trigger is obesity. In December 2021, a study published in the journal Gastroenterology by a team at the German Cancer Research Center suggested that early adult obesity was strongly associated with an increased risk of early-onset colorectal cancer.

Between 2003 and 2020, the study included more than 14,000 people enrolled in bowel cancer screening. At the same time, the study also included people under the age of 55, recruiting a total of 747 patients and 621 matched healthy control groups, with an average age of 48.4 years and 48.7 years, respectively.

Both groups reported reporting weight information starting at age 20 and counting at intervals of 10 years until about 10 years before visiting, and the results showed that the prevalence of overweight and obesity increased steadily with age.

The study found that even after adjusting for multiple potential confounding factors, a higher body mass index (BMI) was strongly associated with the development of early-onset colorectal cancer. Patients who were obese at age 20, 30, and about 10 years before presentation were 1.88 to 2.56 times more likely to develop early-onset colorectal cancer in healthy controls.

In addition, a 2021 study published in JNCI Cancer Spectrum, the top journal in the field of oncology, found that factors such as more intake of red meat (pigs, cattle and sheep, etc.), lower education and excessive alcohol consumption were related to the increased incidence of colorectal cancer in people under 50 years of age.

However, the researchers from the Lancet paper also suggest that more in-depth research is still needed to fully identify and understand the complex interrelationship between exposure to risk factors and the increased risk of colorectal cancer, so as to make targeted prevention recommendations.

Is early screening useful?

Compared with late-onset colorectal cancer, patients with early-onset colorectal cancer are often diagnosed with a progressionary phase. The above paper from The Lancet explains that part of the reason may be related to the time interval between the onset of symptoms and a definitive diagnosis.

Patients with early-onset colorectal cancer generally have a longer time interval between the onset of symptoms and a definitive diagnosis than in patients with late-onset colorectal cancer. One possible cause is that the patient ignores the associated symptoms and does not seek prompt medical attention, or delayed assessment of symptoms during community-based medical visits. In addition, people should also abandon the misconception that colorectal cancer only affects the elderly.

Bleeding is a common symptom of early-onset colorectal cancer, and hemorrhoids, especially hemorrhagic hemorrhoids, cannot be ignored. Studies have found that patients with iron deficiency anemia and blood in the stool have an increased risk of early-onset colorectal cancer nearly 10 times. The U.S. Colorectal Cancer Service Task Force therefore recommends that all patients under the age of 50 with symptoms of unexplained bleeding or iron deficiency anemia undergo colonoscopy.

One proven effective way to do this is to lower the recommended age at which to start screening in the average risk population, including those with associated genetic syndromes and family history. Because the study found that about 16% of patients with early-onset colorectal cancer have an associated genetic syndrome, and another 25% have a family history of CRC.

In 2018, the American Cancer Society recommended lowering the age at which screening began from 50 to 45. Other relevant colorectal cancer screening guidelines in the United States have correspondingly lowered the recommended age.

Not just for risky groups, multiple professional associations in the United States have even recommended lowering the starting age of screening for the general population from 50 to 45 years old.

In the 2020 China Guidelines for Colorectal Cancer Screening and Early Diagnosis and Early Treatment, it is also recommended that the general population undergo colorectal cancer risk assessment from the age of 40, and the people assessed as low-risk and high-risk people should be screened for colorectal cancer from the age of 50 and 40, respectively. Screening programmes are preferred for colonoscopy.