Cases of early onset colorectal cancer, affecting individuals aged 20 to 45, have been rising in recent decades. The cause for this increase remains unclear. Dr. Benjamin Musher, medical director of medical oncology at the Dan L Duncan Comprehensive Cancer Center, discussed potential causes and risk factors.
“Although some early onset cancers are caused by genetic factors, the majority of people under the age of 50 who are diagnosed with colorectal cancer do not have an identifiable genetic cause,” said Musher, professor of medicine and holder of the Barry Stephen Smith Memorial Endowed Professorship at Baylor College of Medicine. “We are not sure what’s behind the rising incidence of young-onset colorectal cancer, but we believe environmental factors are largely responsible.”
Risk factors for colon cancer include obesity, inflammatory bowel disease, a history of colon polyps or cancer, family history of colon cancer, known predisposing germline mutations, alcohol consumption, smoking, and a "western diet" high in processed foods and low in fruits and vegetables. However, these do not fully explain the increasing rates among younger individuals. “Unfortunately, none of these factors fully explain the rising rates of colorectal cancer in younger people,” Musher said.
Emerging research suggests changes in gut microbiome as a potential cause. “Emerging data point to changes in the gut microbiome, the bacteria that live in the bowel, as a potential cause of early-onset colon cancer,” he said. “Studies have shown bacterial content in the bowel is different in people with colon cancer compared to the general population.”
Preventive measures can be taken to lower general risk for colon cancer:
Guidelines recommend starting screening at age 45 for those with average risk. For individuals with certain risk factors or conditions, earlier screening is advised.
Certain symptoms like rectal bleeding and stool habit changes may require diagnostic testing. “Rectal bleeding in young individuals may often be attributed to hemorrhoids, but persistent bleeding with or without changes in stool habits should be taken seriously and discussed with your primary care physician or gastroenterologist,” Musher stated.
Musher emphasized adherence to screening guidelines to prevent cancer development. While rates have increased among younger populations, they have decreased among those over 50 due to effective screening practices that detect and remove precancerous polyps before they become malignant.
