South Korea Sees Rising Colorectal Cancer in Under-40s, Prompting Screening Review

A 41-year-old South Korean man who works as a planning director at a company delayed medical evaluation for Bloody stool he noticed early this year. He attributed it to hemorrhoids and postponed a colon examination, only to be diagnosed with stage 3 colorectal cancer after a health screening in January.

Colorectal cancer remains a leading health concern in Korea. It ranks as the third most common cancer and the third leading cause of cancer deaths after lung and liver cancers. Korea sees roughly 35,000 new cases of colorectal cancer each year. When detected early, more than 90 percent of patients survive at least five years, and surgery can often cure early-stage disease without chemotherapy. Once the disease advances or spreads, treatment becomes more complex, though limited metastases to the liver or lungs can still be managed with surgery or ablation in some cases.

The most important feature of colorectal cancer is its progression from precancerous lesions called adenomatous polyps, which grow on the lining of the colon and can become cancerous over time. Experts say the transformation from polyp to cancer typically takes years to more than a decade, which is why colonoscopy can be a powerful preventive tool by removing polyps before they turn malignant.

Korea operates a national screening framework in which adults aged 50 and older are offered a fecal occult blood test, with positive results prompting a diagnostic colonoscopy. The system aims to detect pre-cancerous lesions and early cancers before symptoms appear.

A growing concern is the rising incidence of colorectal cancer among younger people. In Korea, the rate among individuals under 40 is 12.9 per 100,000 people—the highest in the world for that age group. Data from the Health Insurance Review and Assessment Service show that the number of colorectal cancer patients in their 20s and 30s rose by 34.3 percent from 2017 to 2021. Older patients still comprise the majority, but the speed of increase among younger patients is notable.

Experts cite multiple possible factors behind the shift: aging demographics, rising obesity, greater red meat consumption, lower fiber intake, reduced physical activity, and ongoing smoking and alcohol use. Colorectal cancer also has notable genetic risk, meaning those with a family history may face higher risk. The doctors emphasize that earlier and more frequent colonoscopic screening can be crucial for those at elevated risk, and persistent symptoms such as continued blood in stool, changes in bowel habits, unexplained anemia, or unexplained weight loss warrant medical evaluation regardless of age.

For readers in the United States and elsewhere, the case underscores a global public health question: whether screening guidelines should adjust to earlier ages amid rising incidence among younger adults. It highlights the shared emphasis on early detection, the potential impact on health care costs and screening programs, and the ongoing need for public awareness about colorectal cancer symptoms and risk factors.