"Around 2020, the proportion of young colorectal cancer patients in Korea has increased noticeably. The causes are diverse, but we should pay attention to research showing that excessive consumption of beverages high in fructose more than doubled the risk of cancer."
Kim Tae-won, a professor of medical oncology at Asan Medical Center and a leading authority on colorectal cancer, said in an interview with ChosunBiz on the 14th, "Globally, the age group of colorectal cancer patients is trending downward to under 50, and Korea is no exception."
Colorectal cancer is the third most common cancer worldwide. In Korea, it is also the No. 3 cancer by prevalence. According to a recent international study, the early-onset colorectal cancer incidence among Koreans ages 20–49 was 14.3 per 100,000 people, the highest level among those surveyed in 50 countries.
Kim explained, "With the recent 'slow aging' trend, extreme low-carbohydrate diets are in vogue, and this too can promote the activity of certain gut microbes and increase the risk of colorectal cancer."
Kim emphasized, "Among younger people, 70% of the causes of colorectal cancer are environmental factors such as high-fat and low-fiber eating habits, processed meat intake, obesity, lack of exercise, and smoking," adding, "This means most cases can be prevented by changing lifestyle habits." The point is that improving diet and exercising from a young age are important.
The following is a Q&A.
─ The number of young colorectal cancer patients is rising worldwide.
"Colorectal cancer patients in their 40s and 50s are increasing noticeably. This change is consistently observed across multiple papers, national statistics, and hospital data, and it is clearly felt in clinical practice.
An analysis of Asan Medical Center patient data showed an increase in the number of colorectal cancer patients across all age groups from under 40 to over 70. The number of patients rose sharply around 2020 in particular. Combining national statistics and hospital data, the proportion of patients in their 40s to 60s is estimated to have increased by about 15 percentage points from around 20% in 2020.
In the United States, the increase in colorectal cancer was pronounced among those in their early 40s. In the U.S., where the racial makeup is diverse, there have also been reports that relatively young colorectal cancer patients were identified in certain racial groups."
─ What are the main characteristics of young-onset colorectal cancer?
"About 70% of young-onset colorectal cancer patients are known to develop cancer in the left colon. Because the left and right colon differ in structure, function, and pathogenesis, symptom patterns also differ. The left colon is closer to the anus, so early signals such as bloody stools or pain during bowel movements appear relatively clearly, but they are often mistaken for simple hemorrhoids or enteritis. It is important not to miss early signals and to seek care immediately when symptoms occur."
─ What causes colorectal cancer?
"It is widely known that poor eating habits are closely related to colorectal cancer, but fewer people are aware that sugar-sweetened beverages (including drinks with sugar and fructose) are associated with colorectal cancer.
In particular, we should pay attention to research showing that frequent consumption of sugar-sweetened beverages during adolescence significantly increases the risk of early-onset colorectal cancer. It also appears that switching in adulthood to beverages such as artificially sweetened drinks, coffee, or low-fat milk can reduce the risk of colorectal cancer.
Recently, consumption of products containing artificial sweeteners, such as zero-calorie drinks, has increased, but a link to cancer incidence among younger people has not yet been clearly proven. Long-term observation and further research are needed to clarify the relationship between young-onset colorectal cancer and artificial sweeteners. Caution is warranted because becoming accustomed to sweetness can, over the long term, strongly predispose to obesity.
"Heavy drinking also raises the risks of obesity, type 2 diabetes, and colorectal cancer. People who drank no more than one drink a week had twice the likelihood of developing colorectal cancer compared with those who did not. There are also study results showing that the risk increases by about 16% for each daily drink."
According to a cohort study of 95,464 adult female nurses living in the United States published online in 2021 in the international journal Gut, adult women who drank two or more sugar-sweetened beverages a day had twice the risk of colorectal cancer before age 50 (early-onset colon and rectal cancer) compared with adult women who drank less than once a week. There was also a shocking finding that those who consumed one drink a day during adolescence (ages 13–18) had about a 32% increased risk of colorectal cancer before age 50.
According to a paper published in 2023 in the domestic Journal of Clinical Oncology, an analysis of health data for about 5.66 million adults ages 20–49 showed that moderate drinkers (10–30 g a day, equivalent to 1–2 shots of soju or 1–2 cans of beer a day) had a 9% higher risk than light drinkers, and heavy drinkers (30 g or more, equivalent to three or more shots of soju or three or more cans of beer a day) had about a 20% higher risk of early-onset colorectal cancer.
─ Many young colorectal cancer patients are diagnosed late.
"The tendency for cancer diagnoses to be delayed among younger age groups is consistently reported. Several studies show that younger patients take an average of four months from symptom onset to diagnosis, compared with about 2.5 months for patients 50 and older. A major reason is that younger people do not consider the possibility that 'I could have cancer.'
In particular, the symptoms of colorectal cancer (abdominal pain, bloody stools, changes in bowel habits) are similar to those of hemorrhoids or irritable bowel syndrome, making misjudgment easy. Busy social lives can also delay hospital visits. Whether cancers in young patients are biologically more aggressive varies by study."
─ Is the prognosis good if colorectal cancer is found early?
"If colorectal cancer is detected early and treated, outcomes are very good. For this reason, we recommend colonoscopy every five to 10 years after age 45. For men and women 50 and older, we recommend an annual fecal occult blood test and, if abnormalities are found, a colonoscopy or double-contrast barium enema. Early colorectal cancer does not present symptoms, so screening is essential."
─ Why are you sending a warning message about extreme low-carbohydrate diets?
"Researchers at the University of Washington School of Public Health analyzed the association between biological age and the risk of early-onset cancer (diagnosed before 55) using data from 148,724 people registered in the UK Biobank.
The analysis found that those born after 1965 had a 17% higher risk of accelerated aging compared with those born in 1950–1954, and for each one standard deviation increase in the degree of accelerated aging, the risk rose by 42% for early-onset lung cancer, 22% for gastrointestinal cancer, and 36% for uterine cancer. Accelerated aging may be one cause of the increase in early-onset cancers.
However, extreme low-carbohydrate diets are in vogue, and these too can promote the activity of certain gut microbes and increase the risk of colorectal cancer, warranting caution."
─ All cancer patients inevitably experience mental and physical pain. The psychological pressure is especially high for young cancer patients.
"When someone is diagnosed with cancer at a relatively young age, such as in the 40s, the psychological shock of accepting it is greater. The risks of depression and career interruption also increase. The problem is that young cancer patients are difficult to protect institutionally. In the current national health checkups, colorectal cancer screening targets those 50 and older, leaving those under 40 in a blind spot for screening.
The United States lowered the starting age for screening to 45 to reflect the increase in early-onset colorectal cancer patients. In Korea, national screening is provided for stomach cancer and breast cancer from age 40, and colorectal cancer also needs its screening criteria adjusted to around 45. For early detection, colonoscopy should be encouraged more proactively."
─ Are treatment approaches different for young colorectal cancer patients?
"The treatment principles themselves are not different. However, in younger age groups, we use more proactive and aggressive treatment strategies to maximize the possibility of a cure. Recently, personalized treatment strategies based on genetic test results have become standard in colorectal cancer.
For example, in patients diagnosed with left-sided colorectal cancer who are RAS wild type without EGFR gene mutations, anti-EGFR antibody–based therapies such as cetuximab are often chosen as first-line treatment. This therapy induces a rapid and deep tumor response. Whether to operate is determined by comprehensively considering the number and location of metastatic lesions, vascular structures, and the degree of chemotherapy response."
─ What is the most important clinical criterion in the treatment of metastatic colorectal cancer?
"In the past, many metastatic colorectal cancer patients were deemed difficult to operate on, but recently, we combine neoadjuvant chemotherapy to increase the likelihood of surgery. The treatment approach varies depending on the pattern of metastasis. If metastatic lesions are few and in operable locations, immediate resection can be performed, but if lesions are numerous or in complex locations, we first reduce tumor size and number with chemotherapy and then consider surgery.
The key criteria in this process are the speed of response to chemotherapy and the effect of tumor reduction. Shrinking tumors increases the chance of surgery. For this, a multidisciplinary collaboration system involving internal medicine, surgery, and radiation oncology is essential."
─ What preparations are needed at the national level?
"We need to broadly publicize the importance of early cancer diagnosis through campaigns and education programs. In particular, outreach is needed so that early signals of colorectal cancer, such as bloody stools, are not easily overlooked.
Young cancer patients face various issues beyond treatment, including financial burdens, career interruptions, and fertility preservation. Programs at the hospital or national level must be established to support them. It is important to build systems that help patients not only survive but also plan their lives after treatment.
Young-onset cancer is not necessarily more aggressive or worse in prognosis. If found early and treated appropriately, the likelihood of a cure is sufficiently high. In clinical practice, more active research is needed to identify the causes of colorectal cancer among younger people."