The rectal cancer that caused singer Ahn Chi-hwan to lose 15 kg: "The first sign was in the 'bathroom'"

[Financial News] Interest in rectal cancer is growing after singer Ahn Chi-hwan revealed that he was diagnosed with stage 3 rectal cancer more than a decade ago and endured grueling treatment that caused him to lose more than 15 kg.
Ahn Chi-hwan recently appeared on MBN's "Kim Ju-ha's Day and Night" and cited his cancer treatment as the pivotal event that changed his music and life. “People around me used to say I was sharp and strict,” he said. “After cancer treatment, I thought, ‘I should become a little more generous’ and ‘I should broaden my perspective a little more.’”

Colorectal cancer is a malignant tumor that develops in the colon or rectum, and treatment and management vary depending on where it occurs. According to national cancer registry statistics released in 2026, there were 32,601 cases of colorectal cancer in 2023, accounting for 11.3% of all cancers and ranking third. Cases were 1.4 times more common in men than in women. By age group, people in their 60s accounted for 26.6%, followed by those in their 70s (20.0%) and 50s (19.7%).
Professor Kim In-kyung of the Colorectal Cancer Center at Seoul St. Mary's Hospital's Cancer Hospital (colorectal surgery) explained, “The rectum is located deep within the narrow pelvis and lies next to several organs, including the bladder, prostate and uterus. During surgery, it is important to remove the cancer completely while preserving bowel, urinary and sexual function as much as possible.”
If the cancer is close to the anus, doctors must carefully consider whether the anus can be preserved, and in some cases a stoma may need to be created. Depending on the cancer's stage and location, chemoradiation or chemotherapy may also be given before surgery to shrink the tumor and reduce the risk of recurrence.

The main symptom is a change in bowel habits. Stools may become thinner, constipation and diarrhea may alternate, and a feeling of incomplete evacuation may persist after a bowel movement. Bright red blood may appear on the stool, or there may be dark red blood or mucus in the stool. Continued bleeding can cause anemia and fatigue, while advanced cancer can lead to weight loss and reduced appetite.
However, these symptoms can also occur with hemorrhoids, anal fissures or inflammatory bowel disease, making them difficult to distinguish based on symptoms alone; there may also be no symptoms in the early stages. Professor Kim emphasized, “Don’t assume blood in the stool is due to hemorrhoids or dismiss changes in bowel habits as a simple digestive problem. If symptoms recur, you should undergo tests such as a colonoscopy at a colorectal surgery department.”
To help prevent colorectal cancer, it is advisable to reduce red meat and processed meat and eat plenty of fiber-rich foods such as vegetables, fruit and whole grains. Regular exercise, maintaining a healthy weight, and avoiding alcohol and tobacco can also help lower the risk.
Regular screening is also essential. Under the National Cancer Screening Program, people aged 50 and older are screened annually with a fecal occult blood test, and further tests such as a colonoscopy are recommended if the result is positive. If someone in your family has had colorectal cancer or you have a history of inflammatory bowel disease, consult a healthcare professional to determine when and how to be screened. If you have blood in your stool or a change in bowel habits, seek medical care regardless of when your next screening is due.


[email protected] Jung Myung-jin, Medical Correspondent Reporter